There is growing international pressure for Zimbabwe's president, Robert Mugabe to step down.
Zimbabwe has declared a national emergency over an outbreak of cholera, which has killed at least 565 people.
The collapse of health systems and the water supply in the capital, Harare, are considered the major reasons for the epidemic, which has begun to spread into neighbouring South Africa and Botswana.
The British prime minister, Gordon Brown, has urged the world to tell Mr Mugabe "enough is enough" amid growing concern over the country's cholera outbreak.
He says the crisis, which has claimed nearly 600 lives, has become an international emergency.
Aid groups are warning that half the country's population, five million people, may need food aid in the coming months.
Mr Brown did not explicitly call for Mr Mugabe to step down, but said world leaders should stand together to defend human rights and democracy in Zimbabwe.
The American Secretary of State, Condoleezza Rice, said on Friday it was well past time for Mr Mugabe to leave office.
She said a "sham election" has been followed by a "sham process of power-sharing talks".
African leaders call for Mugabe to go
Archbishop Desmond Tutu says President Mugabe must resign or be sent to The Hague for indictment for "gross violations".
The South African Nobel Prize winner also told Dutch television that Mr Mugabe should be removed by force if he refuses to go.
He told the Nova programme: "I think now that the world must say: 'You have been responsible, with your cohorts... for gross violations, and you are going to face indictment in The Hague unless you step down.'"
Archbishop Tutu said Mr Mugabe had ruined "a wonderful country", turning a "bread-basket" into a "basket case".
Mr Mugabe and opposition leader Morgan Tsvangirai agreed in September to share power to tackle an economic crisis, but they are unable to agree on the allocation of cabinet posts.
On Thursday, Kenya's Prime Minister Raila Odinga said African governments should oust Zimbabwe's leader.