Relations between the United States and Russia were visibly tense during a U.N. Security Council meeting Sunday on the situation in Georgia, with the U.S. accusing Russia of seeking regime change in Georgia.  Washington is a staunch ally of Georgia, which Moscow accuses of causing a humanitarian catastrophe in the breakaway region of South Ossetia. Many South Ossetians hold Russian nationality, and Russia has sent troops into the region.  From United Nation's headquarters in New York, VOA's Margaret Besheer has more.

At the rare Sunday session of the council, called jointly by the United States and Georgia, U.S. Ambassador Zalmay Khalilzad questioned Russia's motives in sending some 10,000 troops into South Ossetia in recent days to prevent Georgia from reasserting control over the Russian-backed breakaway region.

"Russia has claimed that its military operations were intended to protect its peacekeepers and the civilian population in South Ossetia," said Zalmay Khalilzad. "Yet, its reaction goes far beyond any reasonable measures required to do so. Indeed, its escalation of the conflict has been the immediate cause of increased loss of innocent life and humanitarian suffering."

Khalilzad said Russia's expansion of the conflict to another separatist region of Georgia - Abkhazia - and attacks on areas around Georgia's capital, Tblisi, "suggest other motives and objectives." He also accused Russia of obstructing the withdrawal of Georgian forces from South Ossetia.

He said the United States has begun consulting with other like-minded members of the Security Council and would soon introduce a resolution calling for an immediate cease-fire. If such a resolution were strongly critical of Russia's role in the crisis, Moscow would likely use its veto power to quash it.

Russia's ambassador, Vitaly Churkin, responded to the U.S. accusations, calling charges that Russia is targeting civilians and conducting a "campaign of terror" against the Georgian population, "unacceptable" and "propaganda" that had no place in the council. He said Moscow is not obstructing the withdrawal of Georgian troops from the conflict zone.

Churkin said charges that Moscow is refusing international mediation are false, and pointed to several conversations between Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State Condoleezza Rice over the last few days.

Khalilzad seized on that and said the two top envoys' latest telephone conversation "raised serious concerns about Russia's objectives" in Georgia.

"In that conversation, Foreign Minister Lavrov told U.S. Secretary of State Rice that a democratically elected president of Georgia - and I quote -  'must go.' I quote again: 'Saakashvili must go.' This is completely unacceptable and crosses the line," he said. "I want to ask Ambassador Churkin, is your government's objective regime change in Georgia? The overthrow of the democratically elected government of Georgia?"

Ambassador Churkin's response was swift.

"Your interesting reference to the diplomatic telephone call - this confidential call between our minister and your secretary of state," said Vitaly Churkin. "I would like to say straight away, that regime change is an American expression. We do not use such an expression. I'm encouraged by the fact that you have referred to this publicly - I suggest that this means this is an interesting idea and that you are ready to bring this forward to the public platform."

Ambassador Khalilzad was not satisfied.

"I want to restate my question to Ambassador Churkin, he did not answer my question," he said. "Is the goal of the Russian Federation to change the leadership of Georgia?"

"I suggest that I gave a complete response," said Churkin. "Maybe the ambassador was not listening when I gave my response? Maybe he did not have his earpiece on? I suggest that I gave a full response to that question."

The U.S. ambassador was also strongly critical of Russia's refusal to call for an immediate and unconditional cease-fire. Russia's envoy repeated his country's demands that Georgian forces must withdraw from South Ossetia and agree to sign an accord saying Tblisi will not use force with the breakaway republic before it would agree to a cessation of hostilities.