Dmitry Medvedev (L) wants to improve Russia's presence in Latin America
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.
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.
The joint exercises are due to begin at sea on 1 December
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.