Russia and Venezuela have signed an agreement on a $4 billion loan for the oil-rich Latin American partner to buy Russian weaponry, Venezuelan leader Hugo Chavez said on Thursday.

The loan agreement was signed during a snap visit by Russian Deputy Prime Minister Igor Sechin to Caracas on Thursday in view of Chavez’s deteriorating health. The 57-year-old Venezuelan leader has been fighting cancer since June.

“Two billion will be provided next year and another two billion in 2013,” Chavez said.

In August, a Russian diplomatic source signaled Russia’s willingness to extend the loan. “Considering the current election campaign in the country, this loan would mean the opportunity to support our key ally in the region,” the source said in a reference to the 2012 presidential elections in Venezuela.

Venezuela is a leading importer of Russian arms. Between 2005 and 2007, Caracas signed $4 billion worth of arms deals with Russia to buy Sukhoi fighter jets, combat helicopters, and small arms. Chavez’s government also secured a $2.2-billion loan in 2010 to purchase Russian T-72 tanks and S-300 air defense systems.

Venezuela has been seeking a loan of another $6.5 billion from Russia for infrastructure development. Finance Minister Jorge Giordani said in August he would visit Moscow for negotiations in the near future.

The two countries are also interested in oil cooperation. A group of Russian energy firms including Gazprom, Rosneft, TNK-BP, Surgutneftegaz and LUKoil formed an oil consortium chaired by Sechin in 2008 for projects in Venezuela.

Moscow said it would invest $12 billion in Venezuelan oil production in the next ten years.