Much of the world dismissed Zimbabwe's elections last Friday as a sham.
Tsvangirai defeated Mugabe in the first round of the presidential election in March, but subsequently pulled out of the run-off vote, saying nearly 90 of his supporters had been killed and thousands injured in violence he blamed on Mugabe's supporters.
Call for dialogue
The MDC leader's comments on Wednesday came after Mugabe hailed the AU's proposal of dialogue, describing it as an echo of the 84-year-old leader's own call.
"The government is ready for dialogue with whoever, a dialogue for national unity in Zimbabwe," Sikhanyiso Ndlovu, the information minister, said.
International pressure on Mugabe has mounted, with the EU repeating on Wednesday that Tsvangirai must be the head of any new government, despite a warning by Thabo Mbeki, the South African president, not to impose a solution from outside.
Mbeki, chief mediator for Zimbabwe, said it was not for outsiders to dictate the composition of a government that will have to deal with the world's highest inflation rate and widespread food shortages.
|Mbeki is against a solution for Zimbabwe
from outsiders [AFP]
The Zimbabwe crisis dominated the AU summit in the Egyptian resort of Sharm el-Sheikh.
Botswana called for Zimbabwe to be suspended from both the AU and the 14-nation Southern African Development Community (SADC).
The summit ended with a call for Mugabe and Tsvangirai "to initiate dialogue".
Tsvangirai had previously held out the possibility of Mugabe remaining as a ceremonial head of state under a rewritten constitution, but analysts are sceptical about the possibilities of a deal between the two rivals.
Abdoulaye Wade, the Senegalese president, said Mugabe had snubbed the idea of sharing power with the MDC after it was floated by Mbeki in closed-door talks at the summit.
"He [Mugabe] told me this is not possible, that he has his supporters," said Wade.
"I reminded him that the MDC is a real force and that if a prime minister had to be chosen by his level of representation, it could only be Tsvangirai."