South Africa's president was ousted by his own party this weekend.
Mugabe and Tsvangirai agreed Monday to a deal that splits the government, but keeps the military under Mugabe.
As dispute persists in wake of presidential election, the country seems poised between negotiated settlement and outright civil war.
Even in Africa, pressure is mounting for Thabo Mbeki to increase pressure on Zimbabwe's president.
The African Union is expected to discuss the issue in Egypt Monday, one day after Mugabe declared a 'sweeping victory' in Friday's presidential runoff, which was widely condemned as a sham.
The opposition's pullout from Friday's vote raises pressure on Zimbabwe's leader.