Amid rising tensions over Georgia, U.S. officials are increasingly concerned that Russia is moving to rebuild one of the most dangerous features of the old Soviet Union's security structure -- its alliance with Cuba.
Moscow has been signaling that it wants to restore a long relationship with Havana that included not only economic ties, but also military and intelligence cooperation. The relationship brought the world to the brink of nuclear war during the Cuban missile crisis of 1962, when Russia secretly installed nuclear missiles on the island.
U.S. officials believe that Russian statements are partly bluster, intended to dissuade the United States and its allies from moving the NATO alliance and military equipment, including missile defense sites, closer to the Russian border. And some experts question how interested Cuba is in rebuilding close ties with Russia.
But at a time when Russia has intervened forcefully in Georgia and is extending the global reach of its rebuilt military, some senior officials fear it may not be only bluster.
Russia "has strategic ties to Cuba again, or at least, that's where they're going," a senior U.S. official said recently, speaking, like others, on condition of anonymity because of the sensitive implications of the assessments.
The officials said they doubted the Russians would risk stationing nuclear bombers on Cuba. But some believe that Moscow might seek to restore its once-energetic intelligence cooperation with Havana, and to resume limited military cooperation, possibly including refueling stops for aircraft and warships.
In the current environment, such contacts would make U.S. officials uneasy, serving as a reminder of a military relationship between Havana and Moscow that stretched from the Cuban Revolution in 1959 until a weakened, post-Soviet Russia finally closed a massive electronic intelligence complex in Lourdes near Havana in 2001.
One senior military officer said a return of Russian ships or planes could force additional U.S. deployments in the region. But the Bush administration and Pentagon declined to comment publicly on the implications.
"It is very Cold War retro," said a government official. "The topic could be reminiscent of the Cuban missile crisis, and that is a chapter that people don't want to revisit."
The Russian Defense Ministry dismissed a report in the newspaper Izvestia in July that quoted an unidentified Russian official as saying the government intended to begin basing Tupolev Tu-160 Blackjack and Tupolev Tu-95 Bear nuclear bombers in Cuba.
However, the report was taken seriously enough in Washington that Gen. Norton A. Schwartz, the new Air Force chief of staff, said during his Senate confirmation hearing at the time that sending the bombers would cross a "red line in the sand."
Last month, Secretary of State Condoleezza Rice complained about Russia's increasing reliance on its military to remind the world of its power. She criticized Russia's military advance into Georgia, a former Soviet republic, and its increasingly frequent patrols by long-range nuclear bombers in U.S.- and NATO-patrolled ocean lanes near northern Europe, Alaska and elsewhere.
As it rebuilds forces that withered during the impoverished 1990s, Russia also has been looking for new air and naval bases far from home. It is negotiating with Syria to resume use of naval bases in Tartus and Latakia, Russian officials have said. There has also been talk in Moscow of approaching Vietnam about using Cam Ranh Bay.
Russian Prime Minister Vladimir Putin in late July sent one of his closest aides, Deputy Prime Minister Igor Sechin, and a large delegation to meet with Cuban President Raul Castro. The meeting was primarily about economic cooperation, including possible oil exploration off Cuba. But Russian officials made it clear that they were exploring resumption of other aspects of the relationship as well.
Nikolai Patrushev, who is secretary of the Russian Security Council and former director of the FSB, the domestic successor agency to the KGB, met with the Cuban defense and interior ministers on the trip. Afterward, the council issued a statement saying that the two countries planned "consistent work to restore traditional relations in all areas of cooperation."
Afterward, Putin said, "We need to reestablish positions in Cuba and in other countries."
Some Russian analysts remain skeptical of the Kremlin's intentions, seeing the whispers of renewed military activity in Cuba as a tactic meant to rattle the United States.
Russian officials "understand that the restoration of even an intelligence-gathering base in Lourdes would be a declaration of a new Cold War on the part of Russia," said Alexander Golts, defense analyst with the online publication Yezhednevny Zhurnal. "The Kremlin will never do it, because they cannot afford it."
Despite talk of a return to the Cold War, Golts noted, Russia spends 2.7% of its gross domestic product on defense -- unlike the Soviet Union, which at the height of the Cold War spent 40%.
Although several Bush administration officials who have been hawkish on Russia say they find the Cuba ties worrisome, other U.S. officials say the threat should not be overstated.
"The old days are gone, and people need to keep a sense of perspective," said one U.S. official. "That said, I wouldn't assume these [Cuban and Russian intelligence] services never talk to each other."
That official said Cuban intelligence activities posed a concern even without rekindled Russian ties.
"They were and are aggressive on their own," he said. "If anything, the years that have passed since the end of the Soviet Union have convinced the Cubans that, when it comes to intelligence, they themselves are the only people on whom they can rely."
Since becoming president, Raul Castro has generally avoided provoking the United States, said Brian Latell, a former CIA analyst and Cuba specialist. Latell said he was skeptical that Castro would want to be caught in the middle of the rekindled U.S.-Russian rivalry.
"Why go out on a limb for Putin?" asked Latell, who has written a book, "After Fidel," about Cuba's political transition. "I'm not sure I can discern why the Cubans would want to get themselves wrapped around these great power issues."
Latell added, though, that he was ready to believe that the Cubans would cooperate on intelligence and would resume limited military contacts, such as refueling of aircraft.
The 28-square-mile Russian electronic surveillance complex at Lourdes was Russia's largest such base overseas, and reportedly had as many as 1,500 Russian engineers, technicians and military personnel working there. Less than 100 miles from Key West, Fla., its position made it ideal for snooping on the U.S.
The Russian government ended its involvement there in 2001 because of its high cost as well as the strain it exerted on U.S.-Russian relations.
Mark Hackard, assistant director of the Nixon Center in Washington, said Russia's moves grew out of its sense that, although it has given ground on security again and again since the 1990s, it has received little in return from the United States and its allies. Yet, there are limits to how far the Russians will extend their military, he said.
"They're not seeking a new superpower standoff around the world," Hackard said. "They do want primacy in the former Soviet sphere."
Times staff writers Julian E. Barnes in Washington and Megan K. Stack in Moscow contributed to this report.