(Adds details of court case)

By Cris Chinaka

HARARE, April 4 (Reuters) - Zimbabwe's ruling party on Friday backed President Robert Mugabe to fight an expected runoff vote against opposition leader Morgan Tsvangirai, confirming that he was determined to hang on to power.

Earlier this week there were suggestions Mugabe was badly wounded and would step down after his ZANU-PF party lost control of parliament for the first time, facing him with the biggest crisis of his 28-year rule.

But a five-hour meeting of the ZANU-PF politburo decided the former guerrilla leader would fight back and use his considerable presidential powers in an effort to defeat Tsvangirai in a runoff.

A senior party official said the Zimbabwe Electoral Commission would schedule the vote, suggesting it would be changed from the statutory three weeks after election results are issued.

Presidential results have still not been released, six days after the election.

Civil society organisations charged on Friday that Mugabe was trying to delay the re-run for three months to buy time to regroup and ensure victory.

Tsvangirai's Movement for Democratic Change (MDC) says it won the presidential vote and he should be declared president, ending Mugabe's uninterrupted rule since independence in 1980.

ZANU-PF and independent projections say that although Tsvangirai has won, he has fallen short of the absolute majority needed to avoid a runoff.

"We deliberated the rerun, there will be a rerun if ZEC (Zimbabwe Electoral Commission) compels us," said party administration secretary Didymus Mutasa.

"FREEDOM FIGHTERS"

Mutasa said parliamentary votes would be recounted in disputed areas -- a move Mugabe opponents say is a bid to redress the balance in ZANU-PF's favour. Mutasa said the party would go to court over what it alleged was bribery of electoral officials in some places.

Mugabe faces deep discontent as Zimbabwe suffers the world's highest inflation rate of more than 100,000 percent, a virtually worthless currency and severe food and fuel shortages.

Liberation war veterans -- a potent force backing former guerrilla leader Mugabe -- attacked the opposition for claiming victory.

"These are all provocations against us freedom fighters," veterans' leader Jabulani Sibanda told a news conference.

He said the veterans would repel any attempt by white farmers to reclaim properties seized by Mugabe. "It now looks like these elections were a way to open for the re-invasion of this country (by the British)," he said.

The state-owned Herald newspaper said there were reports of white farmers threatening to grab back land.

Critics say the handing of the farms to inexperienced farmers and Mugabe cronies is a key reason for Zimbabwe's economic collapse.

IMPATIENCE

Constitutional lawyers said a re-run had to be held three weeks after results and not three weeks after last Saturday's election, as previously thought.

The MDC, reflecting growing impatience in Zimbabwe at the delay in issuing presidential poll results, said it had filed an application asking a high court in Harare to order the immediate release of the results.

"It will be heard at 10 tomorrow morning (0800 GMT Saturday)," MDC spokesman Nelson Chamisa said. "We want an urgent release of the results, within four hours of the court order."

Analysts believe Mugabe will try to ensure victory in the second vote by using militias and powerful security forces to cow MDC supporters in the interval before the runoff.

A statement by civil society organisations in Harare said they had "reliable knowledge" that Mugabe intended to extend the interval before a runoff "using disputed and autocratic presidential powers".

The statement read by human rights lawyer Lovemore Madhuku expressed "gravest concern at the unacceptable delay in the release of poll results".

Two foreign journalists were arrested on Thursday night for reporting the elections without accreditation. Police said the journalists, one American and one British, would appear in court on Saturday.

The U.S. State Department said another American, working for an election monitoring organisation, had also been arrested.

The White House said it was troubled by the arrests and called for a swift resolution of the post-election stalemate.

"Journalists and NGOs should be permitted to go about their business," White House spokesman Gordon Johndroe told reporters at the NATO summit in Bucharest. (Additional reporting by Nelson Banya, Muchena Zigomo, MacDonald Dzirutwe and Stella Mapenzauswa; writing by Barry Moody; editing by Andrew Roche) (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com)

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