The international rift over how to deal with Zimbabwe widened yesterday after the African Union rejected proposals for tougher action against the regime even as President Bush joined calls for Robert Mugabe to step down.

“It is time for Robert Mugabe to go,” Mr Bush said in Washington. “Across the continent, African voices are bravely speaking out to say, 'Now is the time for him to step down'.”

But the African Union made clear that it would support a resolution only through talks. “Only dialogue between the Zimbabwean parties, supported by the AU and other regional actors, can restore peace and stability to that country,” a spokesman for President Kikwete of Tanzania, the AU chairman, said.

South Africa also maintained that the answer for Zimbabwe was power sharing. “There should be no political point-scoring and games played when what is really needed right now is support,” Ayanda Ntsaluba, a South African Foreign Ministry official, said. He added that Zimbabwean leaders needed to work across the political divide to solve the country's problems.

Sending peacekeeping troops or removing Mr Mugabe by force, as proposed by figures including Raila Odinga, the Kenyan Prime Minister, and Archbishop Desmond Tutu, were simply not options, he added.

Mr Mugabe's spokesman accused the West of using the cholera outbreak to try to bring down the President. “We won this country through the barrel of the gun and we will defend it the way we won it,” George Charamba said.

The international discord is nevertheless lacking one voice - that of US president elect Barack Obama, who has not last commented about the humanitarian disaster in Zimbabwe five months ago.

A spokeswoman for the President-elect's transition team indicated yesterday that she would be willing to issue a statement on his behalf.

Although Mr Obama has been keen to avoid second-guessing the White House on foreign policy issues and emphasised that there can only be “one president at a time”, this does not explain a prolonged period of silence that now stretches back to June 24.

This apparent reluctance to join the fray is matched by that of Hillary Clinton, his nomination for Secretary of State. This week her Senate office referred requests for a comment on the subject to a statement made on June 23.

Expectations for America's first black president are high in Africa. Not only was his father from Kenya, where much of his extended family still live, but he also visited the continent three years ago, when he took courageous stances criticising South Africa's record on HIV/Aids and its quiet diplomacy towards Zimbabwe.

Mr Obama's election last month was greeted warmly by Zimbabwe's opposition leader Morgan Tsvangirai, who said that his fellow citizens would “appreciate the true value of a vote, the preciousness of a poll that is conducted openly and fairly, and a result that is respected by all”.

Mr Mugabe offered his own congratulations, adding: “Those of us in developing countries cherish the hope of working with your administration as we pursue our programmes and policies to develop our societies.”

No one is suggesting that the President-elect is likely to take him up on this offer. Mr Obama's June statement made plain his view that the Zimbabwean Government is illegitimate.

He said that unless fresh elections were held, the US and other countries should tighten “targeted sanctions” and “pursue an enforceable, negotiated political transition in Zimbabwe that would end repressive rule”.

Most observers expect there to be little change in the policy pursued by Mr Bush's Administration, which has largely taken its lead from Britain, where a colonial past and family ties ensure that Zimbabwe receives more attention than elsewhere in the West.

Mark Bellamy, a former US Ambassador to Kenya, said: “There has been an assumption that Obama will be more engaged with Africa. This is not necessarily the case. He has a lot of other issues on his plate and even in Africa I don't think Zimbabwe will be top of the agenda.”

Susan Rice, Mr Obama's foreign policy adviser nominated for the post of UN ambassador, has stated that one of her goals will be to prevent future genocides.

*Lord Malloch-Brown, the Africa Minister, will travel to South Africa tomorrow for talks on the cholera crisis, a spokesman said yesterday.

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