The United States on Friday pushed for an immediate cease-fire in a fast-unfolding conflict between Russia and Georgia over the breakaway Georgian province of South Ossetia.

The White House said President Bush discussed the situation with Russian Prime Minister Vladimir Putin while both leaders were in Beijing for the start of the Olympics. And Secretary of State Condoleezza Rice called the parties involved in hopes of ending the fighting, and made plans to send a U.S. envoy to the region.

“We urge all parties, Georgians, South Ossetians and Russians, to de-escalate the tension and avoid conflict,” White House press secretary Dana Perino said from Beijing. “We are working on mediation efforts to secure a cease fire and we are urging the parties to restart their dialogue.”

She said Bush was getting regular updates on the situation and reiterated that the U.S. “supports Georgia’s territorial integrity.”

In Washington, State Department spokesman Gonzalo Gallegos would not name the envoy who would be sent.

A U.S. official, speaking on condition of anonymity because no official announcement had been made, said the envoy was Deputy Assistant Secretary of State Matthew Bryza, a specialist on the region. The timing of the trip was unclear because of the changing situation.

The scramble by U.S. diplomats came as Georgian troops launched a major military offensive to regain control over South Ossetia. The fighting prompted a furious response from Russia, which vowed retaliation and sent a column of tanks into the region.

It was the worst outbreak of hostilities since the province won de facto independence in a war that ended in 1992.

A Russian military officer said that 10 Russian peacekeepers were killed and 30 wounded when their barracks were hit in Georgian shelling. Russia has soldiers in South Ossetia as peacekeeping forces, but Georgia alleges they back the separatists.

Vasil Sikharulidze, Georgia’s ambassador to Washington, said in an interview, “We are asking our friends, and the United States among them, to somehow to try to mediate and try to persuade Russia to stop this military aggression and invasion of Georgia.”

“What we heard is that the State Department and the entire administration is deeply concerned and that they are heavily engaged with Russia trying to de-escalate the situation,” he said.

At a luncheon for world leaders in Beijing, Bush talked to Putin about the fighting, a White House spokesman said, without giving details.

Department of Defense officials have had some contact with Georgian authorities, Pentagon spokesman Bryan Whitman said Friday, adding that the U.S. is monitoring the situation closely. Whitman said Georgia has not requested any assistance from the U.S., but he would not provide details on the discussions that have occurred.

He said he does not believe U.S. military officials have had any contact with the Russians.

According to Whitman, the U.S. has about 130 trainers in Georgia, including a few dozen civilians, who are all working to prepare the Georgian forces for their next deployment to Iraq. All of those U.S. trainers, he said, have been accounted for, none have been injured, and there are currently no plans to pull them out of the country.

He said the trainers are in the Tbilisi area, but would not say exactly where.

Both major U.S. presidential candidates also weighed in.

Republican John McCain said Russia should immediately withdraw all forces from sovereign Georgian territory.

“What is most critical now is to avoid further confrontation between Russian and Georgian military forces. The consequences for Euro-Atlantic stability and security are grave,” he said, calling for the international community “to establish a truly independent and neutral peacekeeping force in South Ossetia.”

Democrat Barack Obama said Georgia and Russia must show restraint and avoid a full-scale war.

“All sides should enter into direct talks on behalf of stability in Georgia,” he said in a statement.