Speaking on a visit to Tanzania, Mr Bush said the people of Zimbabwe deserved a government that recognised their "basic human rights".
Mr Bush had thrown his weight behind a possible power-sharing deal between President Mwai Kibaki and his chief opponent, Raila Odinga, as a way out of the political impasse.
Mr Bush also wants to allay concerns about a new military command he wants to base in Africa to work with African militaries to deal with trafficking or terror
Earlier, Mr Bush signed a $698m deal with Tanzanian President Jakaya Kikweteto to reduce poverty. 
Mr Bush urged the US Congress to renew his global programme to combat Aids. He also wants it doubled from $15bn to $30bn
