The music streaming wars have officially begun.

Google on Wednesday announced Google Play Music All Access, a streaming music service for smartphones, tablets and desktops. All Access, which launches in the U.S. on Wednesday, allows users to stream "millions" of songs, create personalized radio stations and discover music based on their music preferences, according to the company.

"This is radio without rules," Chris Yerga, Android's engineering director, said when he introduced the service at Google's annual I/O conference in San Francisco. "It's as lean back as you want to as or as interactive as you want it to be."

The service, which will be available for $9.99 per month after a monthlong free trial, competes directly with Spotify, the 5-year-old streaming music service that launched in the U.S. in 2011, as well as Pandora, the Internet radio giant.

Unlike All Access, which has a monthly fee, Spotify uses a "freemium" model; users can listen, with ads, for free on their desktop computers, pay $4.99 to listen ad-free, or pay $9.99 to stream and download unlimited music on multiple devices.

Pandora, which has 200 million registered users, also offers its ad-supported radio service for free. Users can upgrade to Pandora One for $36 annually to get higher-quality and ad-free music.

Spotify, which is now available in 28 countries, has more than 24 million active users. Six million of those, according to the company, are paying subscribers.

Spotify touts its large catalog -- the service says users have access to 20 million songs with 20,000 more added each day -- as one of its greatest assets. A spokesperson from Google did not elaborate on Yerga's assertion that All Access's music library has "millions" of songs, and Google did not specify which music labels have made their content available on All Access.

Spotify, which has been aggressively courting new subscribers ahead of Google's announcement, has deals with EMI, Sony Music, Universal and Warner Music, among others.

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• Linus Upson

  Linus Upson, vice president of engineering at Chrome, speaks as volunteers play Google Racer on different devices at Google I/O 2013 in San Francisco, Wednesday, May 15, 2013. (AP Photo/Jeff Chiu)

• Sundar Pichai

  Sundar Pichai, senior vice president, Chrome and Apps at Google, holds a Google Chromebook Pixel laptop computer at Google I/O 2013 in San Francisco, Wednesday, May 15, 2013. (AP Photo/Jeff Chiu)

• Hugo Barra

  Hugo Barra, vice president, Android Product Management at Google, holds a Samsung Galaxy S4 “Google Edition” while speaking at Google I/O 2013 in San Francisco, Wednesday, May 15, 2013. (AP Photo/Jeff Chiu)

• Vic Gundotra

  Vic Gundotra, senior vice president, engineering for Google, speaks at Google I/O 2013 in San Francisco, Wednesday, May 15, 2013. (AP Photo/Jeff Chiu)

• Sundar Pichai

  Sundar Pichai, senior vice president, Chrome and Apps at Google, speaks at Google I/O 2013 in San Francisco, Wednesday, May 15, 2013. (AP Photo/Jeff Chiu)

• Sundar Pichai

  Sundar Pichai, senior vice president, Chrome and Apps at Google, speaks about the 900 million android users at Google I/O 2013 in San Francisco, Wednesday, May 15, 2013. (AP Photo/Jeff Chiu)

• Hugo Barra

  Hugo Barra, vice president, Android Product Management at Google, speaks at Google I/O 2013 in San Francisco, Wednesday, May 15, 2013. (AP Photo/Jeff Chiu)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Google senior vice president of Android, Chrome and Apps Sundar Pichai is seen silhouetted against a video presentation as he speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Hugo Barra, Google vice president of product management for Android, speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Google senior vice president of Android, Chrome and Apps Sundar Pichai speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Attendees use camera phones to take pictures before the start of the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Attendees line up to enter the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Larry Page, Google co-founder and CEO speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Attendees line up to enter the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Chris Yerga, Google engineering director for Android, announces the new Google Play Music All Access as he speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: An attendee uses a computer to sign in for the Google I/O developers conference on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Larry Page, Google co-founder and CEO speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Larry Page, Google co-founder and CEO speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Chris Yerga, Google engineering director for Android, speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Larry Page, Google co-founder and CEO speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Sundar Pichai, Google senior vice president of Android, Chrome and Apps, holds a Google Chromebook Pixel as he speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: An attendee uses a camera to take pictures before the start of the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Attendees look on as Larry Page, Google co-founder and CEO speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Larry Page, Google co-founder and CEO speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Larry Page, Google co-founder and CEO speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Attendees look on during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: An attendee wears Google Glass as he watches the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Hugo Barra, Google vice president of product management for Android, holds a Samsung Galaxy S4 Google Edition as he speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Linus Upson, Google vice president of Chrome, talks about Google Racer as he speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Attendees look on as Hugo Barra, Google vice president of product management for Android, is seen on a video screen as he speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Attendees look on during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Hugo Barra, Google vice president of product management for Android, holds a Samsung Galaxy S4 Google Edition as he speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: Larry Page, Google co-founder and CEO speaks during the opening keynote at the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)

• Google Developers Event Held In San Francisco

  SAN FRANCISCO, CA - MAY 15: A man stands next to an oversized Google map marker pin as attendees wait to enter the Google I/O developers conference at the Moscone Center on May 15, 2013 in San Francisco, California. Thousands are expected to attend the 2013 Google I/O developers conference that runs through May 17. (Photo by Justin Sullivan/Getty Images)