U.S. Ambassador Zalmay Khalilzad exchanged sharp words with the Russian ambassador on Sunday, accusing Moscow of seeking "regime change" in Georgia and resisting attempts to make peace after days of fighting have left hundreds of civilians dead.

Khalilzad disclosed during a U.N. Security Council session that Russian Foreign Minister Sergei Lavrov had told U.S. Secretary of State Condoleezza Rice on Sunday morning "that a democratically elected president of Georgia — and I quote — must go."

Khalilzad turned to Russian Ambassador Vitaly Churkin repeating the exchange and saying, "This is totally unacceptable and crosses the line." He then asked whether the country was attempting to overthrow Georgian President Mikhail Saakashvili.

"Is your government's objective regime change in Georgia, the overthrow of the democratically elected government of Georgia?" he said.

Churkin confirmed there had been a "confidential phone call" between Lavrov and Rice, but did not directly answer Khalilzad.

"I'd like to say straightaway that regime change is an American expression," Churkin said. "We do not use such an expression. But sometimes there are occasions, and we know from history, that there are different leaders who come to power, either democratically or semi-democratically, and they become an obstacle."

Lavrov later told reporters in Moscow that Rice had misinterpreted his remarks. Referring to Georgia's president, Lavrov said Russia can no longer view "a man who issued orders to commit war crimes" as a negotiating partner and therefore "without the departure of Saakashvili it is impossible to stop the conflict in South Ossetia."

But Georgia's ambassador, Irakli Alasania, told the council it was "Russia's intention to erase Georgian statehood, to exterminate Georgian people." He later told The Associated Press that the conversation between Lavrov and Rice about Saakashvili confirms "something that we believed always that Russia had in mind."

Churkin, in turn, accused Georgia of waging "genocide" against South Ossetians. He said Russia will only act in self-defense. "Let's state clearly that we are ready to put an end to the war, that we will withdraw from South Ossetia, that we will sign an agreement on nonuse of force," Churkin proposed.

However, diplomats said major fighting continued in many areas.

The conflict began when U.S.-allied Georgia began an offensive to regain control over the breakaway province of South Ossetia overnight Friday. Georgia launched heavy rocket and artillery fire and air strikes that pounded the provincial capital of Tskhinvali.

In response, Russia launched overwhelming artillery shelling and air attacks on Georgian troops. On Sunday, Russian jets targeted an aircraft-making plant near the airport on the outskirts of Tbilisi, the capital of the former Soviet republic.

Georgia borders the Black Sea between Turkey and Russia and was ruled by Moscow for most of the two centuries preceding the 1991 breakup of the Soviet Union. Both South Ossetia and, Abkhazia, another breakaway region nearby that has often been a sore point between Russia and Georgia, split away from Georgia after fighting in the early 1990s and have run their own affairs without international recognition.

Both separatist provinces have close ties with Moscow, while Georgia has deeply angered Russia by wanting to join NATO.

The Security Council's session Sunday was the fourth meeting in as many days. Council members broke off their three-hour meeting Sunday to return to private negotiations outside council chambers. The council had no more plans to take up the matter until Monday at the earliest.