UNITED NATIONS — A plea by Zimbabwean opposition leaders to increase international involvement in their country’s political crisis is being rebuffed by three members of the U.N. Security Council.

America and several other council members expressed support for sending a U.N. representative on a fact-finding mission to Zimbabwe, as the council met yesterday on the African nation for the first time since the March 29 elections. Such a mission could increase the international pressure on President Mugabe to relinquish his post or at least release the complete results of the election, which opposition members say he lost.

At the council yesterday, Britain also suggested imposing a voluntary arms embargo against Harare. But in London there were reports that the sanctions now in place are being violated, and Zimbabwe’s opposition leaders also accused U.N. agencies of abetting Mr. Mugabe’s regime.

“The will of the people needs to be respected in Zimbabwe,” President Bush said at a press conference in Washington. “It is clear that they voted for change, as they should have, because the — Mr. Mugabe has failed the country.”

The secretary-general of Zimbabwe’s largest opposition party, the Movement for Democratic Change, Tendai Biti, was in New York yesterday, and urged council members in one-on-one meetings to intervene. “Zimbabwe is basically a war zone,” he told reporters, added that neighboring countries steering the diplomacy through the Southern African Development Community have failed to remedy the crisis.

The U.N. undersecretary-general for political affairs, Lynn Pascoe, briefed the council behind closed doors on what he called Zimbabwe’s “worst humanitarian crisis since independence.” Mr. Pascoe said Secretary-General Ban “would be happy to cooperate with SADC” and the African Union in Zimbabwe, a suggestion that American and British diplomats said could lead to deeper United Nations and Security Council involvement.

But South Africa, China, and Russia rebuffed the idea, diplomats said. “The Africans are working, so the U.N. should support the Africans, not replace them,” the Chinese ambassador to the United Nations, Wang Guangya, told The New York Sun. The South African ambassador, Dumisani Kumalo, said any U.N. involvement depended on the government of Zimbabwe, which is controlled by Mr. Mugabe.

“We find that there are certain people and certain countries that have decided to play pingpong with our people,” Mr. Biti said. His party’s leader, Morgan Tsvangirai, won the election, Mr. Biti said, but the United Nations “is not too responsive to non-state actors, and we are a non-state actor at this point.” Mr. Wang, for his part, denied that Mr. Biti asked to meet with China’s U.N. diplomats.

In London yesterday, members of Parliament accused British-based Barclays Bank of providing “personal banking services” to up to four of Mr. Mugabe’s top aides, who reaped the benefits of the government’s land grabs from white farmers in Zimbabwe, the Daily Telegraph reported. Barclays allegedly bypassed economic sanctions by using its Harare branch, which is mostly Zimbabwean-owned.

A member of Britain’s House of Lords, Daphne Park, Baroness of Monmouth, recently retracted her accusation that Zimbabwe-based representatives of the U.N. Development Program accepted land from Mr. Mugabe. In the retraction, however, the baroness said she was not backing down from her “reservations about the UNDP’s relations with the government of Zimbabwe.”

Yesterday Mr. Biti accused unnamed U.N. agencies based in Zimbabwe of being “complicit” in Mr. Mugabe’s government. “If there was no subjective and incestuous relationship with the regime, a lot of things could have been done now,” he said. “It’s quite ironic, for instance, that our office at 444 Nelson Mandela Avenue can be turned into an internal refugee center, yet the offices of one of the U.N. agencies is less than 400 meters away.”