"I'm very happy to be that age," Mugabe said at a meeting of the Southern African Development Community in Pretoria. "I am happy that God has looked after me."
After years of international criticism, the European Union is resuming aid to the country and has already lifted sanctions on some senior government figures, while Mugabe has taken up the rotating chair of the African Union.
"An immense amount of Western pressure to step down and reverse some of his policies -- and he's done neither."
When he came to power in 1980, Mugabe was a hero of the fight against white minority rule in the former Rhodesia.
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He won international praise for his declared policy of racial reconciliation and for extending education and health services to the black majority.
But critics say that over the following decades he turned the "breadbasket of southern Africa" into a basket case, with human rights, justice and democracy trampled.
Ostracised by the West, but still respected as a liberation hero by other African leaders, Mugabe has remained defiant.
"Down with imperialism. There was no country in Africa that was opposed to Zimbabwe becoming chair (of the AU), not even a single one," he boasted after his appointment last month.
Mugabe once quipped that he would rule his country until he turned 100 -- and he shows every sign of trying to achieve that goal.
He has recently purged his ruling ZANU-PF party of senior ministers and officials seen as allies of his former deputy, Joice Mujuru, who was accused of plotting to succeed him.