UNITED NATIONS — Using well-coordinated U.N. Security Council speeches, Britain, America, and Secretary-General Ban are seeking to initiate a diplomatic sequence that could resolve the post-election crisis in Zimbabwe.

Prime Minister Brown of Britain, at a high-level meeting at the council yesterday, welcomed Mr. Ban’s offer to dispatch international observers to Zimbabwe to oversee a second round of elections, if necessary. “No one thinks” President Mugabe, who is clinging to power after 28 years in office, won the first round last month, Mr. Brown said.

The choreography of the initiative — in which Mr. Ban was to offer international observers, while Mr. Brown and Ambassador Zalmay Khalilzad of America would then enthusiastically recommend that international players and Zimbabwe respond to it — almost came undone during yesterday’s meeting.

Mr. Ban, who met earlier in the day with President Lee of South Korea, was late for the morning session. In the earlier meeting, Mr. Lee invited Mr. Ban for a state visit, a U.N. source who spoke on the condition of anonymity said. Mr. Ban, who is South Korean, may have an opportunity to go to his homeland in July if he attends a G–8 summit in Japan.

Yesterday’s council meeting was convened by President Mbeki, who was seeking to cement his legacy prior to relinquishing power in South Africa next year by sealing a cooperation agreement between the United Nations and the African Union. Instead, he faced speeches about Zimbabwe. With Mr. Ban running late, Mr. Mbeki was about to give Mr. Brown the floor, depriving the British premier of the opportunity to accept Mr. Ban’s offer.

It was just at that time that Mr. Ban came in, warning that “the credibility of the democratic process in Africa is at stake” and adding that, if Zimbabwe holds a second round of elections, it should be conducted in a “fair and transparent manner, with international observers.”

Mr. Mbeki, who is seen as an ally of Mr. Mugabe, has opposed outside intervention in Zimbabwe, preferring diplomatic negotiations led by neighboring southern African leaders. In his speech to the council, Mr. Mbeki did not mention Zimbabwe, nor did most other African leaders, leaving the topic to be raised by their Western counterparts.

“No one thinks, having seen the results at polling stations, that President Mugabe has won this election,” Mr. Brown told council members. “A stolen election would not be a democratic election at all.”

Mr. Mugabe has refused so far to release the results of the March 29 vote. Opposition leaders have accused him of trying to conceal his defeat and say they have fears he will steal the next round as well — fears that could be allayed if outside observers are present.

“We are not saying there should be a second round,” a British official and former deputy U.N. secretary-general, Mark Malloch Brown, said. “You don’t build cheat on cheat.”

But it was clear yesterday that the choices presented to Mr. Mugabe were to step down, agree to a second round under outside supervision, or face further international pressure.

“We think it is very important that the election not be stolen, that the results are released in a way that has credibility and reflects the will of the people of Zimbabwe,” Mr. Khalilzad told reporters. “We support what the secretary-general said as part of that effort to send international observers.”

Wire services reported that Mr. Mbeki said last week in Harare that “there is no crisis” in Zimbabwe. Yesterday the president said he had no idea where the quote came from. “The very fact that there is mediation like this,” he said, shows that “something is wrong.” But he stopped short of defining the situation as crisis.