HARARE, Zimbabwe –A third day of talks over Zimbabwe’s governance wound up on a conflicting note yesterday amid reports that President Mugabe and the leader of an opposition faction had reached a power-sharing agreement.

Shortly after the talks concluded, officials from Mr. Mugabe’s party and the main opposition movement said the two sides had agreed on the plan, but a spokesman for the splinter group later denied the claim.

The reported agreement excludes Morgan Tsvangirai, the leader of the main Movement for Democratic Change. He won the first round of presidential elections in March but boycotted the runoff to protest widespread violence against opposition supporters.

Such an agreement would likely prompt protests from the West and some African governments for allowing the 84-year-old Mr. Mugabe to cling to his increasingly autocratic 28-year reign that has driven his once thriving nation to economic ruin.

President Mbeki of South Africa, who mediated the talks, did not comment to reporters as the third day of talks concluded.

But Welshman Ncube, a spokesman for the splinter faction of the Movement for Democratic Change, denied reports that his leader, Arthur Mutambara, had signed an accord with Mr. Mugabe.

“It’s a lie,” he said.

The officials from the ruling party and the main opposition movement led by Mr. Tsvangirai said that Messrs. Mugabe and Mutambara both endorsed the plan. They spoke on condition of anonymity because mediator Mr. Mbeki has insisted on confidentiality.

Mr. Mutambara himself would not comment before Mr. Mbeki issued a statement.

Mr. Tsvangirai’s faction has 100 seats in Parliament, just ahead of Mr. Mugabe’s ruling ZANU-PF’s 99. Mr. Mutambara’s faction holds only 10. He agreed to form a parliamentary alliance with Mr. Tsvangirai after the March elections, but if he now switches allegiances, it will give the majority to Mr. Mugabe’s party. However, it is uncertain whether all his lawmakers will follow him into the ZANUA-PF fold.

Mr. Mugabe won the run-off of Zimbabwe’s presidential elections after Mr. Tsvangirai boycotted it to protest widespread violence. Mr. Tsvangirai won the first round, though not by an outright majority.

Mr. Mugabe brushed off questions as he left the hotel in the capital Harare after three days of grueling talks, saying: “I’m sleepy.”

But he denied that the negotiations had failed. “Talks will never collapse as long as we have tongues,” he said.

The key stumbling block has been how much power Mr. Mugabe is willing to cede to the opposition movement.

Mr. Tsvangirai has said he could work with moderates from Mr. Mugabe’s ZANU-PF party, but not with Mr. Mugabe.