By: Angus Shaw, THE ASSOCIATED PRESS

HARARE, Zimbabwe - The presidential run-off election pitting President Robert Mugabe against opposition leader Morgan Tsvangirai will not take place in the next few weeks as required by law, the head of the electoral commission said in an interview published Sunday.

Tsvangirai announced on the weekend that he would participate in a run-off against Mugabe - but insisted the vote be held, as the law requires, within 21 days of the May 2 announcement of results from the first vote.

However, the chairman of the Zimbabwe Electoral Commission, George Chiweshe, said government officials need more time to prepare for the run-off.

"It was ambitious for the legislature to think 21 days would be enough," Chiweshe was quoted as saying in the state-run Sunday Mail newspaper.

Chiweshe confirmed the 21-day provision in electoral law, but said there were legal provisions to extend the period. Government officials have said the electoral commission has up to a year to hold the second round.

However, Chiweshe seemed to indicate the voting would be held sooner than that.

"We want to make it clear we intend to hold the run-off at the earliest date because the period set by the legislature shows that it should be held as soon as possible," he told the newspaper.

It took the commission more than a month to announce results from the disputed March 29 presidential election. Tsvangirai, leader of the opposition Movement for Democratic Change, contends he won the first round outright and claims the official figures are fraudulent.

But the opposition leader, who has remained abroad since the vote because of threats to his life, said Saturday in South Africa that he would take the risk of returning to Zimbabwe to contest a run-off vote.

Mugabe has been accused of orchestrating violence against the opposition since the first round, raising questions about whether a run-off would be free or fair.

Twenty-two people have died and 900 have been tortured in post-election violence, according to the Zimbabwe Association of Doctors for Human Rights. The group said 40,000 farm workers have been displaced in an effort to prevent them from voting in the run-off.

Fifty-six opposition activists were arrested in Shamva, north of Harare, opposition lawyer Alec Muchadehama said Sunday.

The opposition accused the electoral commission of being biased toward Mugabe, and predicted that more opposition supporters would come under attack to prevent them from voting during any further delay.

Tendai Biti, secretary general of the MDC, raised concerns about the "deepening humanitarian crisis" in Zimbabwe.

He disputed the electoral commission's claim that there were legal grounds for delaying the run-off. "They don't have the discretion to move the date," he said.

Mugabe's ruling ZANU-PF, meanwhile, already has launched its run-off campaign.

On Sunday, presidential spokesman Patrick Chinamasa said the party will not allow an opposition victory.

"Mugabe, at 84, do you believe he is fighting for himself? That's what the people of Zimbabwe should understand," Chinamasa told reporters in Harare. "He is fighting blatant attempts at recolonizing Zimbabwe."

Chinamasa said the party's campaign would be based on "land, empowerment, freedom and sovereignty."

Mugabe, who has held power in Zimbabwe since the country gained independence from Britain in 1980, was once was hailed for promoting racial reconciliation and bringing education and health care to the black majority.

But in recent years he has been accused of holding power through intimidation and vote-rigging, and of overseeing his country's economic collapse.

Tsvangirai assured regional leaders that if he were to win the presidency, he would respect Mugabe's place in Zimbabwe's history.

Tsvangirai told reporters in the Angolan capital Saturday that Mugabe would be treated as the "father of the nation" in the interest of building peace and stability in Zimbabwe.

That appeared to indicate a softening of his stance, after telling The Associated Press in an interview last month that he believed the Zimbabwean people would press for Mugabe to stand trial for crimes against humanity.