Analysis: U.S. has few moves against Russia.

WASHINGTON - Even as it accuses Russia of using "disproportionate" force in the conflict over Georgia's rebel South Ossetia province, the United States finds itself with few diplomatic or military options to deter Moscow's ferocious air and ground assault.

In fact, most of the key cards, including the power to veto any United Nations resolutions, were held by Russia, which appeared to be using the crisis to ram home to the United States and its allies that it will not accept further expansion of NATO. Both Georgia and the former Soviet republic of Ukraine are seeking to join the alliance.

The Russian invasion "sends a message to all of the countries in the former Soviet space that Russia is resurgent and is willing to flex its muscles," said David Philips, an expert with the Atlantic Council.

"This is Russia's assertion of power," said retired Army Gen. Wesley Clark, a former top NATO commander.

Jim Jeffrey, a national security official at the White House, said from Beijing yesterday that the United States has "made it clear to the Russians that if the disproportionate and dangerous escalation on the Russian side continues, that this will have a significant long-term impact on U.S.-Russian relations."

But U.S. calls for a truce, which were echoed by the European Union again yesterday, appeared to have little immediate impact.

State-run media quoted Prime Minister Vladimir Putin as defending Russia's intervention as "totally legitimate" and accusing Georgia of committing "genocide." He said Georgia wanted to join NATO in order "to drag other nations and peoples into its bloody adventures."

Putin's comments reflect Russia's longstanding anger over NATO expansion, U.S. support for the admission of Georgia and Ukraine to the alliance, and the Bush administration's plan to build missile-defense facilities in the Czech Republic and Poland.

Russia is also still fuming over NATO's intervention against Serbia during its 1999 crackdown on ethnic Albanian separatists in Kosovo, and U.S. and European recognition earlier this year of Kosovo's independence over the Kremlin's objections.

Envoys yesterday frantically sought a cease-fire. President Bush, in Beijing pressing international mediation, reached out to French President Nicolas Sarkozy, who heads the European Union. The two agreed on the need for a cease-fire and a respect for Georgia's integrity, White House spokesman Gordon Johndroe said.

But beyond diplomacy and high-level statements, there appeared little the United States and its allies could do to, such as extending NATO combat air patrols to Georgia as was done in 2002 to deter Russian interference in Lithuania.

"There are already Russian aircraft over Georgia, so the chances of direct engagement [between Russian and NATO aircraft] is very high," Clark said.

"If you are in Moscow and you are looking at the tools that the U.S., NATO and the EU have, what are they?" asked a former senior State Department official who requested anonymity to speak more freely. "Nobody is going to send troops, so you are going to get away with it."

Some experts worried that Russia would not halt its offensive until it drove Georgian troops out of South Ossetia and another Moscow-backed separatist enclave, Abkhazia, and forced the pro-U.S. government of President Mikhail Saakashvili out in favor of a pro-Moscow leadership.

Ivo Daalder of the Brookings Institution said Secretary of State Condoleezza Rice should "get off the phone and onto a plane and make it completely clear to Moscow that our relationship depends on what they do from here on out."

But Bush must walk a careful line with the Kremlin, whose cooperation the United States requires on a range of pressing issues.

Russia is involved in international efforts to resolve the Iranian nuclear crisis, and could use its U.N. Security Council veto to block further sanctions that the United States and its European partners want to slap on Tehran for rejecting the latest plan to encourage negotiations.

Moscow is also part of the six-nation talks on eliminating North Korea's nuclear weapons program.

Russia is a major supplier of natural gas to Europe - its top eight customers are all NATO members, according to the U.S. Energy Department - and has already shown that it is prepared to reduce supplies over disagreements.