The Cold War may be over, but U.S. and Russian soldiers are expanding outposts in this mountainous former Soviet republic about 3,200 miles east of NATO headquarters in Brussels and nearly 2,000 miles from Moscow.

The U.S. opened its base three years ago as a launching pad for troops and cargo heading into Afghanistan. Two years later, with the Americans showing no signs of leaving, Russia opened its own base. Now, Moscow is quadrupling the number of its troops, while the American garrison is crawling with bulldozers and trucks, as Washington spends $10 million replacing tents with sturdier quarters.

Officially, Russia has welcomed the U.S. presence as a reflection of a new partnership against a common enemy: Islamic extremists. Washington, in turn, has praised Moscow for enhancing cooperative security efforts in this volatile corner of Central Asia.

But the cooperation is limited largely to words. The current U.S. base commander has never met his Russian counterpart, troops are mostly forbidden to venture outside their respective gateposts, and military flights are scrupulously segregated.

The bases here are symbols of a new rivalry between East and West for influence over the lands of Russia's old empire. More than a decade after it ended, the global Cold War standoff has been supplanted by competition for political and economic hegemony along Russia's vast frontier stretching from the Baltic Sea to China.

After the collapse of the Soviet Union in 1991, a weakened Russia initially turned inward and the West moved rapidly into the faded superpower's sphere of influence. But now, armed with $50-a-barrel oil and a determination to protect its interests, a newly confident Kremlin is reasserting centuries-old claims.

The competition extends far beyond Kyrgyzstan. The U.S. also has military bases in neighboring Uzbekistan and has sent military trainers to Georgia, where Russia has two bases. Moscow's Baltic Sea fleet sails from a sliver of Russian territory between two new North Atlantic Treaty Organization members, Poland and Lithuania; NATO planes now patrol the skies over former Soviet republics to Russia's west.

The Caspian Sea basin, with its more than 200 billion barrels of oil, is seen by both Russia and the U.S. as a zone of strategic interest. Russia is using its energy reserves to maintain influence in the small, newly independent countries of the Baltic and Caucasus regions.

And now, the struggle between pro-Moscow and pro-Western forces is playing out in the disputed presidential election in Ukraine, a territory that for centuries has been central to Russia's sense of itself as a great power.

"As a military man, I see that Russia is surrounded. And I can imagine the reaction of the U.S. if our country were all of a sudden to declare the Gulf of Mexico the zone of our vital interests. We're gritting our teeth," said Russian parliament deputy Viktor Alksnis, a former air force colonel.

"On the other hand, they are mistaken if they think Russia collapsed along with the Soviet Union in the 1990s," he said. "For all the 1,000 years of history of our state, Russia has been like a human heart. It squeezes and unsqueezes. And what we have seen recently is that people who should have looked to Russia as a partner in tackling global problems have instead seen a need to drive the Russian bear back into its den."

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In 2000, Boris N. Yeltsin handed over the Russian presidency to Vladimir V. Putin, a former KGB agent whose youth and aura of strength gave his demoralized and chaotic country a badly needed shot of confidence.

While Putin consolidated his political power, Russia also gained a windfall from rising global oil prices. Now, backed by its energy wealth, $100 billion in gold and foreign currency reserves (growing lately at a rate of $2 billion a week) and an upgraded arsenal of 7,800 nuclear warheads, Putin has broadly reasserted the power of the Russian state.

He has blocked the sale of Russia's biggest oil companies to Western conglomerates, sharply centralized government authority and driven democratic forces to the political margins.

And in the last year or two, it also has become clearer how Putin aims to position Russia in the world at large. Quietly, Russia is regaining a semblance of its historic empire.

By locking in energy contracts, controlling pipelines and buying up regional utilities, the Kremlin now holds a near-monopoly in much of Eastern Europe and the former Soviet republics. Russian businessmen have bought up factories, steel mills and energy companies. Russian interests that back pro-Moscow candidates now represent a powerful political force in nearly every former Soviet republic.

"Until recently, everyone was concerned that Russia, weakened by its internal crisis, was becoming unpredictable," Defense Minister Sergei B. Ivanov said this year. "But now a different kind of Russia is feared: a country which has become stronger and more confident after several years of stability and economic growth."

To some in the West, the scenes now playing out in the Caucasus, Central Asia and the Baltics hark back to the czarist empire's conflicts with other European powers, including Peter the Great's parade through the Baltics; periodic invasions of Poland; and the "Great Game" with Britain for control of Central Asia.