MONROVIA, LIBERIA, MAY 25 -- President Samuel Doe said today that he is ready to step down or hold early elections under international supervision if it would help end a war launched by rebel forces steadily advancing on this capital.

Doe made the offer at a rally the day after his government announced that its forces had won their first victory against the rebels by recapturing the strategic Atlantic port of Buchanan.

It was not possible to confirm the government's claim. Buchanan, Liberia's second city, located about 90 miles southeast of the capital, is this West African nation's main exit point for iron ore, which provides 70 percent of its foreign currency.

Diplomats said they have received conflicting reports on who held Buchanan, Liberia's main port, which rebels took Sunday. Telephone lines to the city were down.

Doe told the pro-government rally that he did not want to remain president if it meant Liberians had to suffer and die. He also said that, if Liberians wished, he would invite international observers and an independent electoral commission to supervise early elections.

Doe did not say when he might hold earlier elections, and the rebel National Patriotic Front of Charles Taylor did not respond immediately to Doe's offer. The two men have refused to hold direct negotiations, as the United States has suggested.

At a news conference today, Deputy Information Minister Moses Washington said 350 rebels had been killed in a government ambush as they tried to infiltrate past Gbarnga, a garrison town 107 miles northeast of Monrovia.

Washington said government forces retook Buchanan after moving in slowly to minimize civilian casualities. He gave no figures on deaths in the fighting.

Forces loyal to Doe had mostly avoided contact with the rebels who invaded from Ivory Coast on Dec. 24. The rebels control Nimba County, where the invasion began, and most of two other counties. Rebel columns have been reported 10 miles from the capital.

International human rights groups have said Doe's troops massacred hundreds of civilians in the fighting, which forced tens of thousands of Liberians to flee to neighboring Ivory Coast and Guinea.