UNITED NATIONS, April 29 (Reuters) - The U.N. Security Council took up Zimbabwe's election standoff for the first time on Tuesday, and Western powers pressed for a U.N. mission or envoy to visit the crisis-stricken southern African country.

Vote checking from Zimbabwe's March 29 presidential poll was put off again on Tuesday, further delaying the day when the world will know if President Robert Mugabe will remain in power in a once-prosperous country that is now in economic meltdown.

France's U.N. Ambassador, Jean-Maurice Ripert, told reporters the fact that the Security Council had met to discuss the crisis sent a signal to Zimbabwe's authorities "that we are looking very carefully at what they are doing."

The U.S. and British envoys said U.N. Under-Secretary General for Political Affairs Lynn Pascoe had told the closed meeting that Zimbabwe was in the midst of its worst humanitarian crisis since independence from Britain.

"He also spoke about a level of political intimidation and violence that I think many council members found quite chilling," British Deputy Ambassador Karen Pierce said.

Pierce said Britain backed the idea of sending a U.N. envoy or fact-finding mission and had raised the possibility of a voluntary arms embargo or moratorium on arms shipments.

Other European countries, Latin American members and the United States also supported sending an envoy, diplomats said, but South Africa, which currently holds the council presidency, said such a move was not a matter for the council.

Pascoe told reporters U.N. Secretary General Ban Ki-moon was willing to "use his good offices" in cooperation with African regional groups that are leading mediation efforts.

South African Ambassador Dumisani Kumalo said, however, the question of an envoy was a matter for Ban to discuss with Zimbabwe.

POWER-SHARING DEAL?

Diplomats have said South Africa was reluctant to have the council take up the issue of Zimbabwe, which President Thabo Mbeki has said should be resolved through quiet diplomacy, but acceded to a demand by several council members last week.

The idea of a U.N. envoy was strongly endorsed by Tendai Biti, secretary general of Zimbabwe's opposition Movement for Democratic Change. In an interview with Reuters, Biti suggested U.N. official Anna Tibaijuka, who visited Zimbabwe three years ago to investigate Mugabe's drive to demolish shantytowns.

In Washington, U.S. President George W. Bush told a news conference: "The will of the people needs to be respected in Zimbabwe, and it is clear that they voted for change as they should have because Mr. Mugabe has failed the country."

MDC leader Morgan Tsvangirai says he won the presidential election outright and there is no need for a run-off, but independent and ruling party projections pointed to a second round to decide the winner.

At a food summit in Geneva, Ban told reporters it was "just unacceptable" that Zimbabwe's leaders had not yet released the results four weeks after the ballot. "We know who is the winner," he added, in an apparent reference to Tsvangirai.

Zimbabwe's U.N. ambassador suggested both sides would need to come up with a power-sharing deal in a national unity government. "There is no way anybody can do without the other," Boniface Chidyausiku told the BBC.

A win for Mugabe, whose ruling ZANU-PF party lost control of parliament in the election, would deepen Zimbabwe's economic collapse, political analysts say, whereas Western powers are likely to pour in aid and investment if victory goes to Tsvangirai.

Severe food, fuel and foreign currency shortages are worsening in Zimbabwe and there are no signs the inflation rate of 165,000 percent -- the world's highest -- will ease.

The Zimbabwe Electoral Commission invited presidential candidates and their agents to verify results from May 1. The process, which had been due to start on Tuesday, could still take another week before a result can be made public.

"This exercise will pave way for the announcement of the result of the presidential election," state radio said in a notice from the commission.

Mugabe has been under heavy international pressure over the delay and even the former guerrilla leader's old regional allies have shown signs of impatience.

Opposition supporters from rural areas described a campaign of arson and brutality against them since the ballot.

Thousands of people have fled their homes and the MDC says more than 15 of its supporters have been killed by ZANU-PF militants. The ruling party denies this.