President Mbeki of South Africa is expected to travel to Harare tomorrow to make one final attempt to push Robert Mugabe into negotiating a settlement with the opposition Movement for Democratic Change, The Times has learned.

Mr Mbeki's decision to travel to Zimbabwe for the second time in a week came after a day of frantic diplomatic activity in which governments worldwide condemned Mr Mugabe for a campaign of violence which forced Morgan Tsvangirai, the opposition leader, to withdraw from this Friday's election run-off.

Britain appeared to be taking the hardest line with diplomats revealed to be circulating a draft UN resolution which declared that - in the absence of a second round of voting - the result of the first round should be made binding. Mr Tsvangirai defeated Mr Mugabe in that contest, held in late March, although by an insufficient margin to win without a second ballot.

Mr Mbeki's impending visit comes after the Zimbabwean President rejected a similar call for national unity last week and reflects the growing pressure by the West on southern African leaders to take a stand against Mr Mugabe, 84.

The opposition says Mr Mugabe and his armed militia are responsible for the deaths of more than 80 activists during the election campaign, which Mr Tsvangirai said left him with no choice but to withdraw. The opposition leader was tonight under the protection of the Dutch embassy in Harare, as threats to his safety increased.

As the fallout to yesterday's withdrawal announcement intensified, British diplomats circulated a draft Security Council statement declaring the government's "campaign of violence" had made a "free and fair" run-off in the presidential election impossible. The Security Council is due to meet tonight.

"Until there is a clearly free and fair second round of the presidential election, the only legitimate basis for a government of Zimbabwe is the outcome of the 29 March 2008 election," the draft statement said.

"The Security Council calls on the Zimbabwean authorities to allow African Union and United Nations envoys to find a peaceful way forward that allows a legitimate government to be formed that reflects the will of the people."

The British proposal faces serious opposition from South Africa and potentially other countries on the 15-nation council, such as Russia and China, that oppose UN intervention in member states.

South Africa moved quickly to signal its opposition to key parts of the British proposal, suggesting the draft favoured Zimbabwe's opposition Movement for Democratic Change.

Dumisani Kumalo, South Africa's UN ambassador, said his country would back a Security Council statement as long as it "edges the process forward".

"It should take into account that we are in a very sensitive stage," he said. "There are talks that are happening between the parties through the mediator in Harare, through South Africa. The parties are talking."

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