Russian President Dmitry Medvedev has described Russian-Cuban ties as "especially intense", after meeting Cuban President Raul Castro in Havana.
He also met the president's ailing brother, former leader Fidel Castro.
Cuba is his last stop on a four-nation tour of Latin America intended to build up Russia's ties in the region.
Mr Medvedev arrived in Havana from Venezuela, where he and President Hugo Chavez signed a deal on nuclear energy and discussed military co-operation.
The Russian president also visited Brazil and Peru.
After meeting his Cuban counterpart, Mr Medvedev told reporters: "We have a systematic dialogue. Our relations have been generally good, but in the past six months they have become especially intense."
Mr Medvedev said he wanted to boost Russia's presence in a region it had previously neglected - a region traditionally of strategic importance to the US.
Russian companies are interested in drilling for oil in Cuban waters and investing in a nickel processing plant.
Cuba is unlikely to want to antagonise the US with President-elect Barack Obama taking office in January, says the BBC's Michael Voss in Havana.
Naval exercises
In Venezuela, Mr Medvedev signed an accord with Mr Chavez to help Venezuela build a nuclear energy plant. Joint gas projects were also approved.
Military co-operation was also high on the agenda of Mr Medvedev's talks with Mr Chavez.
Russian and Venezuelan warships are scheduled to hold joint military exercises later this week.
Russia is already a major arms supplier to Venezuela, with contracts worth some $4.4bn (£2.39bn).
The Russian leader travelled to Venezuela from Brazil, where he and President Luiz Inacio Lula da Silva held talks on boosting trade and technical co-operation.
In Rio de Janeiro, the two presidents expressed their view that the "Bric" countries - Brazil, Russia, India and China - should hold their first summit in Russia in 2009.
Mr Medvedev's visit takes place just a few days after the Chinese president, Hu Jintao, toured several Latin American nations with a view to strengthening ties.
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