Tutu has called on the international community to use the threat of force if necessary to get Mugabe to step down.
"I haven’t changed," he told reporters Saturday. "He’s had an innings. It was a good innings and then he messed up. Let him step down."
Mugabe, in power since independence from Britain in 1980, is accused of destroying the southern African nation’s once-vibrant economy through corruption and mismanagement, and of trampling on the human rights of its people.
Zimbabwe’s main opposition leader, Morgan Tsvangirai, is to be prime minister and Mugabe is to remain president in a unity government expected to be inaugurated next week.
Tsvangirai, under pressure from regional leaders and eager to address Zimbabwe’s growing humanitarian crisis, agreed to join the coalition despite the continued jailing and harassment of dissidents and deep reservations about Mugabe’s willingness to share power.
Tutu, the retired Anglican archbishop of Cape Town, said the deal should be given a chance, "but many are not particularly hopeful." He said Mugabe would have to be closely monitored to ensure the coalition does not turn out to be a "charade."
Tutu spoke seated next to Kumi Naidoo, an international anti-poverty advocate in the 18th day of a hunger strike that aimed to put pressure on Mugabe. Naidoo also expressed reservations about the unity government’s prospects for success, but said "now we need to trust the judgment of the people on the ground in Zimbabwe."
Naidoo called on Mugabe to release political prisoners, allow humanitarian organizations to work freely, and repeal restrictions on free speech and assembly.
In Zimbabwe’s capital Saturday, human rights groups said several prisoners linked to Tsvangirai’s opposition party were at risk of dying in jail. At least three, including a 72-year-old man, were in critical condition, according to doctors who examined them in their cells Friday.
Police are accused of torturing the detainees and have ignored several court orders demanding that the prisoners be sent to private medical facilities.
"We might end up with losing lives. We are very concerned. These people are very sick," said Dr. Douglas Gwatidzo, director of the Zimbabwe Association of Doctors for Human Rights.
On Friday, a judge ended the treason trial of a top Tsvangirai aide, which was seen as a sign that Mugabe’s party wants the coalition to work. Still, scores of opposition members and human rights activists remain jailed in what observers in and outside Zimbabwe say was a crackdown on dissidents as power-sharing negotiations faltered.
Tsvangirai reluctantly agreed Jan. 30 to move forward on a unity government deal without having resolved disputes over Cabinet posts and the treatment of dissidents. The agreement has been stalled since September.
Tsvangirai won more votes than Mugabe in the opening round of presidential balloting last March, but pulled out of a June runoff because of violence against opposition supporters. International observers have called the June runoff a sham.
The standoff since the March vote has kept the country’s leaders from addressing the country’s devastating economic and social collapse. A cholera epidemic has killed more than 3,300 people and infected 60,000 since August and the world’s highest inflation rate has left millions of Zimbabweans dependent on international food aid to survive.