BUENOS AIRES — President Vladimir V. Putin of Russia and his Argentine counterpart signed deals on nuclear energy and other projects on Saturday in an effort to expand his country’s influence in Latin America.

Russia will help build the third reactor of a nuclear power plant in Argentina, Mr. Putin said after meeting with the Argentine president, Cristina Fernández de Kirchner, here on Saturday.

Both leaders said the nuclear projects would be for peaceful purposes.

Russia also hopes to build bases in Argentina for its satellite system and cooperate over the use of military technology, Mr. Putin said, including the use of Russian planes and helicopters in the sector of Antarctica claimed by Argentina. Russian companies may also take part in the construction of two hydroelectric plants here.

On Friday, Mr. Putin brokered deals between Russian and Cuban energy companies in Havana, and waived 90 percent of Cuba’s Soviet-era debt.