HARARE (Reuters) - President Robert Mugabe will chair a meeting of his ruling party politburo on Friday to discuss Zimbabwe's elections, amid uncertainty over whether he will stand in a runoff vote to stay in power.

Senior ZANU-PF official Didymus Mutasa declined to comment on whether the party was planning for a Mugabe runoff against opposition leader Morgan Tsvangirai, although another official said earlier it was ready for a vote and would win it.

"All I can confirm is there is a politburo meeting. That's enough, that's all I can say at the moment," said Mutasa, the party secretary for administration.

Party sources said Mugabe, facing the biggest crisis of his 28-year rule, would chair the meeting.

Analysts said Mugabe was believed to have convened the party leadership to discuss their next move after ZANU-PF's first defeat in parliamentary elections and to gauge how much support there was for him running in a second round.

All the signs are that Mugabe, a liberation war leader still respected in Africa, is in the worst trouble of his rule after facing an unprecedented challenge in the elections because of the collapse of the Zimbabwean economy.

Although five days have passed since the presidential election, no results have been released.

Deputy Information Minister Bright Matonga said earlier the party was ready for a second round, in the strongest indication yet that Mugabe intended to stand, despite calls by the opposition to concede defeat and avoid embarrassment.

"From ZANU-PF's perspective, we are very confident that we've got the numbers, when it comes to a re-run, we're ready for that second round, and we are confident that President Robert Mugabe will win this time," Matonga said.

The opposition Movement for Democratic Change says Tsvangirai won an absolute majority in the presidential vote and no re-run is necessary.

NO CLEAR WINNER

In an interview with Reuters Television, Matonga added: "We think, and it is my assumption...there may not be a clear winner of the presidential one (vote) and it points to a re-run."

In his first public appearance since the March 29 election, Mugabe met the head of an African Union election observer team at his residence in Harare, state television reported.

Asked by about his meeting with Mugabe, Sierra Leone's former President Ahmad Tejan Kabbah told ZTV: "He looked very relaxed, and is of the view that the problems of the country will be resolved amicably, and he is very relaxed about it."

Officials said on Thursday results were expected soon from the senate election. They say the presidential outcome will not be released until after that.

The Senate has 66 seats, six of them appointed by Mugabe. It has the power to block legislation from the lower house.

The Zimbabwean constitution concentrates much power in the president and parliament has been seen in the past as a rubber stamp body.

Respected South African financial daily Business Day reported that Mugabe had admitted to family and advisers that he had lost and was weighing up whether to throw in the towel or contest a runoff against Tsvangirai.

ZANU-PF and independent projections say Tsvangirai will fall short of an absolute majority in the presidential vote and a runoff will be necessary.

Mugabe's aides have angrily dismissed the MDC's claim that it had won the presidential poll.

Final results of the election for parliament's lower house showed the MDC won 99 seats. ZANU-PF won 97 and a breakaway MDC faction won 10. One independent candidate won a seat. The outcome of the senate vote will be issued next.

Mugabe has faced growing discontent with the world's highest inflation rate of more than 100,000 percent, a virtually worthless currency and severe food and fuel shortages.

Hopes of a peaceful transition to power in Zimbabwe helped lift neighbouring South Africa's rand currency on Thursday as investors saw a positive impact on the region.

"I think that (Zimbabwe) certainly has the most influence on the rand at the moment," a Johannesburg-based trader said. "So there is potential for the rand to strengthen further if there is a peaceful transition."

Millions of economic refugees have fled Zimbabwe's misery into South Africa, many of them illegally.

Jonathan Moyo, Mugabe's former information minister who is now an independent in parliament, said authorities were not coping well with defeat. Security chiefs, who have said they would not accept an opposition victory, were anxious.