Their power-sharing deal has raised hopes among Zimbabweans of an end to widespread hardship, but wrangling since they signed their agreement in September has stirred doubts over whether they can work together to bring in aid and investment.

Mr Tsvangirai, 56, was sworn in by Mugabe, 84, who has ruled with his ZANU-PF party since independence from Britain in 1980.

Tsvangirai won a first round presidential poll against Mugabe last year but boycotted a subsequent run-off over violence. He said rescuing the economy would be a top priority and called on the world to help Zimbabwe recover.

Zimbabwe is suffering unemployment above 90 percent, prices double every day, half the 12 million population need food aid and a cholera epidemic has killed nearly 3,500 people.