* Zimbabwe says still needs help with cholera

* WHO says death toll at 792

* Ban urges Mugabe to agree on power-sharing government

By Nelson Banya

HARARE, Dec 12 (Reuters) - A huge international aid effort is needed to help Zimbabwe combat a cholera outbreak that has killed hundreds, the government said on Friday, even though President Robert Mugabe has said it is now contained.

"We need all the support we can get from peace-loving nations," information minister Sikhanyiso Ndlovu told reporters.

The main opposition MDC also called for more help in fighting the epidemic.

Mugabe, under Western pressure to step down as Zimbabwe's economy and health system collapse, had said on Thursday that "we have arrested cholera".

But the United Nations said the death toll, now nearly 800, was rising.

Ndlovu said the media had misrepresented Mugabe's comments, and presidential spokesman George Charamba said they were taken out of context.

The outbreak follows months of violence and political turmoil in Zimbabwe. Coupled with chronic food shortages, it has highlighted the economic collapse of the southern African country.

The health system is ill-prepared to cope and there is not enough money to pay doctors and nurses or buy medicine. The water system has collpased, forcing residents to drink from contaminated wells and streams.

Neighbouring South Africa is worried about conditions as thousands of Zimbabweans cross the border each day.

DEATH TOLL RISING

The World Health Organisation (WHO) said on Friday the death toll from cholera had risen to 792, with 16,700 cases.

"I don't think that the cholera outbreak is under control as of now," WHO spokeswoman Fadela Chaib said in Geneva.

"We are not commenting on President Mugabe's assertion because it's not the place to discuss politics now.

Mugabe, who has ruled Zimbabwe for the past 28 years, has accused Western countries of trying to use the cholera outbreak to force him out of power.

"Now that there is no cholera there is no case for war," he said in Thursday's remarks.

Western leaders and some within Africa have called on the 84-year-old leader to step down as the epidemic compounds Zimbabwe's political and economic crisis.

United Nations Secretary-General Ban Ki-moon urged Mugabe on Friday to agree to a rapid deal on a new government.

Mugabe and opposition leader Morgan Tsvangirai reached a power-sharing deal brokered by regional mediator Thabo Mbeki, South Africa's former president, in September. But they are deadlocked over how to implement it.

The MDC said while it was still committed to the talks, it would not be a part of a unity government unless positions were allocated freely and a new National Security Council was created.

Ban said he had pressed Mugabe in "very tense" private talks two weeks ago in Doha to accept the Sept. 15 agreement.

Asked whether he backed calls for Mugabe to leave office, Ban told a news conference in Geneva: "He should really look for the future of his country and his own people who have been suffering too much and too long from this political turmoil now coupled with very serious humanitarian tragedies.

"I am really appealing and urging him again."

Britain on Friday questioned a U.S. proposal to seal Zimbabwe's borders to hasten the collapse of Mugabe's government, saying the move could have far worse consequences.

Mark Malloch Brown, senior British official for Africa, said if neighbouring countries closed their borders, Zimbabweans would have no escape route and the crises would worsen.

(Additional reporting by Stephanie Nebehay in Geneva and Luke Baker in London, editing by Angus MacSwan)

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