Zimbabwe's ruling party has backed President Robert Mugabe to fight an expected run-off vote against opposition leader Morgan Tsvangirai, ending uncertainty over whether he would try to extend his long grip on power.

A senior party official said last night that the Zimbabwe Electoral Commission (ZEC) would schedule such a vote, suggesting it would be changed from the statutory three weeks after election results.

Civil society organisations claimed yesterday that Mugabe was trying to delay the rerun for three months to give him time to regroup and ensure victory. Zanu-PF agreed on its strategy after a meeting to discuss the biggest crisis of Mugabe's 28-year-old rule.The party lost control of parliament for the first time in last Saturday's election but no official results have yet been released from the presidential vote.

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.

However, Zanu-PF and independent projections say that although Tsvangirai has won, he will fall short of the absolute majority needed to avoid a run-off.

"We deliberated the rerun, there will be a rerun if ZEC compels us," said party secretary Didymus Mutasa.

He added that parliamentary votes would be recounted in disputed areas - an apparent bid to redress the balance in Zanu-PF's favour. He said there had been bribery of electoral officials.

The long delay in announcing presidential votes has fuelled opposition suspicions that Mugabe is trying to engineer a way out of results that went against him.

He faces deep discontent as Zimbabwe suffers an inflation rate of more than 100,000%, a worthless currency and severe food and fuel shortages.

Earlier, liberation war veterans - a force backing former guerrilla leader Mugabe - attacked the opposition for claiming victory. "These are all provocations against us freedom fighters," leader Jabulani Sibanda said.

Analysts believe that 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 run-off.

Meanwhile two journalists, including a New York Times correspondent, were charged with violating the country's media laws and are due to appear in court today, a police spokesman said last night.

The New York Times said its reporter, Barry Bearak, was taken into custody from his hotel in the capital, Harare, where he was covering the election.

The other journalist is British. Both were arrested on Thursday night.

Human Rights Watch called on the Zimbabwean authorities to "immediately allow lawyers to see the two journalists." Zimbabwean authorities are also holding another American, while two other US citizens have been freed, the US State Department said.