Pressure is mounting on South Africa to take responsibility for resolving the crisis in Zimbabwe before a United Nations Security Council meeting this week.
The US said that it was talking to South Africa and other members of the Security Council about how to “start a process that will bring an end to the tragedy that is unfolding in Zimbabwe”.
Lord Malloch-Brown, the British Minister for Africa, who returned from an emergency trip to Pretoria on Friday, said that he detected movement in the South African mood away from the belief that the power-sharing settlement could be implemented and towards a harder line against President Mugabe.
“There is increasingly a view that you are not going to get a deal while Robert Mugabe is President,” he said.
Security Council members will meet in New York today for two days of private talks, with piracy off the coast of Somalia top of the agenda.
The US and Britain, however, will push for discussions on possible measures against Zimbabwe, including the reconsideration of sanctions against the ruling inner circle.
These were rejected in July after Russia reversed its position at the last minute. South Africa also opposed them and China abstained.
The Government of Mr Mugabe made an attempt to force the power-sharing deal into law, issuing a draft constitutional amendment creating the office of prime minister for Morgan Tsvangirai, the leader of the Movement for Democratic Change (MDC).
The Bill appeared to give Mr Mugabe the power to swear in Mr Tsvangirai without the need for parliamentary approval.
The Zimbabwean Justice Minister has threatened to hold fresh elections if Parliament does not pass the Bill promptly.
The MDC dismissed the move, saying that a settlement remained deadlocked over the refusal of Mr Mugabe to relinquish control of key ministries.