Although U.S. officials are publicly playing down the rising tension, a series of conflicts has prompted some within the Bush administration to conclude that, for domestic and geopolitical reasons, Russia is now more comfortable with the U.S. as an enemy than an ally.
The government of Russian President Vladimir V. Putin, flush with petrodollars and increasingly aggressive on foreign policy, has challenged the Bush administration on a wide range of issues just in the last few months. While U.S. officials badly need Russian help in the Middle East and elsewhere, Moscow has bucked Washington on Iran, Kosovo, missile defense, NATO expansion, arms treaties, and governance in its own country.
The acrimonious rhetoric between the two countries is likely to get louder, and some foreign diplomats and analysts fear that in places such as Kosovo and Georgia, the collision of interests could result in violence.
"The trajectory of the relationship has been steadily downward," said Michael McFaul, a Stanford University political science professor and expert on post-Soviet countries. After peaking just after the Sept. 11 attacks, "it's now the worst it's been in 20 years."
On Iran, the Russians at a gathering in Berlin last week resisted U.S. efforts to impose more painful sanctions against Tehran, forcing the Bush administration to settle for much less than what it had been seeking.
The meeting was dominated by wrangling between Russian Foreign Minister Sergei V. Lavrov and Secretary of State Condoleezza Rice, a specialist on Russian and Soviet affairs. It "was not always all that easy," Germany's foreign minister said afterward, describing the heated sessions with diplomatic understatement.
Underlying the mounting friction is Russia's shift in the last few years from a country that once strove for full integration with the West to one that now seeks to serve as an independent power center that can check what it views as the excessive influence of the United States. Russian leaders calculate that opposing an unpopular Bush administration will consolidate their domestic position while helping them gain leadership status abroad.
Bush administration officials say that Russian leaders believe the United States exploited their weak post-Cold War position in the early 1990s.
The Russian view is, " 'We were weak, stabbed in the back, betrayed. But now we're back -- we're strong,' " said a senior administration official, speaking on condition of anonymity when discussing internal assessments.
"They seem to relish fighting with us and accusing us of various things," said the administration official. "They like having an enemy."
In the view of many Russians, the U.S. posture in the world has changed for the worse over the years, and now requires a different response.
"America now reminds me of a person who enters a bar with a gun in his hand and says, 'Look, if you're not tolerant enough, I'll shoot you on the spot,' " said Mikhail G. Delyagin, the chairman of Moscow's Institute of Globalization Studies. "They perceive any sign of dissent as a manifestation of aggression against themselves."
Both sides have compared the other, at least obliquely, to Nazi Germany.
The complaint that the West took advantage of Russia's weakness is reminiscent of grievances "with a bad history in the 20th century," the senior Bush administration official said, referring to accusations made by the Nazis to build domestic support.
Putin laid down a tough line last February in Munich, Germany, when, without mentioning the United States by name, he complained of countries that were trying to expand their world power like the Nazis before World War II.
In public, top U.S. officials soft-pedal their conflicts with Russia, saying that they do not view Russia as an enemy, and pointing out that the two countries are working well on such issues as counter-terrorism and North Korea's nuclear weapons program.
They dismiss a new debate among foreign policy experts about "Who lost Russia?" that follows the lines of the "Who lost China?" debate in the mid-20th century.
"The recent talk about a new Cold War is hyperbolic nonsense," Rice insisted on Wednesday in a speech at the World Economic Forum in Davos, Switzerland.