KINSHASA, Zaire (AP) _ Rebels pressing hard to end Mobutu Sese Seko's 32-year dictatorship have warned foreigners to leave the capital, and U.S. troops across the border in Congo are ready should evacuations be needed.

The rebels have given Mobutu until Sunday to leave office and have threatened to bring their fight to the capital, Kinshasa, if he doesn't. They already control more than a third of the country, mostly in the east, and have encountered little resistance in their quest to topple the president.

With the prospect of civil war coming to Kinshasa, about 1,300 Marines and other U.S. forces were ``at a very high state of awareness and preparedness,'' set to evacuate hundreds of U.S. citizens if necessary, a Pentagon spokesman said Thursday in Washington.

``The Marines ... are standing by and at the ready in the event that they are called upon to help out,'' Navy Capt. Michael Doubleday said.

There are about 500 Americans in Zaire, 320 of them in the capital.

Meanwhile, an increasingly isolated Mobutu _ abandoned by such longtime supporters as the United States and Belgium, its colonial ruler _ has turned to the military to salvage his long and corrosive rule.

Likulia Bolongo, an old army buddy of Mobutu, wore his general's uniform and was saluted by his guards Thursday as he left his luxurious Kinshasa home for his first meeting with the president since being made premier.

Today, Likulia is expected to present 25 new Cabinet ministers for approval by Mobutu. Defense Ministry spokesman Leon Kalima said 10 posts will go to Mobutu supporters, 10 to the camp of ousted Prime Minister Leon Kengo wa Dondo, three to military officers and two to civic leaders.

Kengo was Mobutu's handpicked prime minister, but he was blamed for the army's losses to eastern rebels, and Mobutu was forced to fire him two weeks ago and replace him with the popular opposition leader Etienne Tshisekedi.

Likulia replaces opposition leader Etienne Tshisekedi, whom Mobutu cronies blocked from taking his seat as premier Wednesday. The move, coming after Mobutu had given into domestic and international pressure and appointed Tshisekedi, angered the president's overseas allies.

``Mobutuism has no future, and now we have to see how to get to a transitional government,'' Belgian Foreign Minister Erik Derycke said in Brussels.

The White House called Thursday for rebel-government negotiations on a transitional government.

A senior aide to Tshisekedi promised further resistance, and said the Tshisekedi administration _ which considers itself Zaire's legitimate government _ would seek to try Mobutu for high treason.

Joseph Yaone said Tshisekedi's path would continue to be non-violent. ``We don't have to prove ourselves against barbarians.''

Likulia's convoy arrived at Mobutu's heavily guarded palace, overlooking the rapids of the Zaire River, just as a bugle call marked the noon hour.

The pomp recalled Mobutu's rise to power in 1965, when the United States and Belgium saw the eager and capable young colonel as the key to stabilizing Zaire and thwarting Soviet expansion in the region. The friendship faded with the end of the Cold War and Mobutu's mismanagement of Zaire's mineral-rich land.

The Belgian and U.S. ambassadors met with Likulia on Thursday.

``I think that this country needs, very badly, change,'' U.S. Ambassador Daniel Simpson said afterward. ``What you need is responsible elected government.''

The rebels said they were approaching Kinshasa and called on foreign nationals to evacuate the capital, according to a radio report monitored in nearby Gabon. Diplomats in Kinshasa said they were not taking the warning seriously.

Doubleday said the Marines are on board the amphibious warship USS Nassau off the coast of Zaire. There also are U.S. troops in Brazzaville, Congo, across the river from Kinshasa, and in Libreville, Gabon, who would help in an airlift from the region.