US President George W Bush has called for "free and fair" elections to be held in Zimbabwe.
Speaking on a visit to Tanzania, Mr Bush said the people of Zimbabwe deserved a government that recognised their "basic human rights".
Earlier, Mr Bush signed a $698m deal with Tanzanian President Jakaya Kikwete to reduce poverty.
Mr Bush is in the east African nation on the second leg of a six-day five-nation tour of the continent.
The deal will help improve roads, power and water supplies and comes as part of the Millennium Challenge compact, which makes grants to countries which stick to democratic principles and sound economic policies.
President Bush said free and fair elections in Zimbabwe were in the interest of its people.
"It happens to be in the interest of the world as well," he said at a joint news conference with President Kikwete, who is the new head of the African Union.
Zimbabwe is due to hold presidential and legislative elections at the end of March.
PRESIDENT BUSH'S ITINERARY
Benin - Cotonou: arrival ceremony, meets president
Tanzania - Dar es Salaam: meets president, tours hospital; Arusha: tours hospital, textile mill and girls' school
Rwanda - Kigali: meets president, visits genocide memorial
Ghana - Accra: meets president, state dinner
Liberia - Monrovia: meets president, visits university
Western countries say the last elections in 2002, which saw President Robert Mugabe returned to office, were not free and fair. Mr Mugabe is standing again for the ruling Zanu-PF party.
The political stalemate and violence following Kenya's disputed election in December was also on the agenda during Mr Bush's visit to Tanzania.
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.
He said his discussions with the Tanzanian leader had focused on "how best we can help the process. Not what we should do to dictate the process."
Kenya's Foreign Minister, Moses Wetangula, speaking on Sunday, warned other countries not to try to force a deal on Kenya.
"We encourage our friends to support us and not to make any mistake of putting a gun to anybody's head and saying 'either or' because that cannot work," he told reporters.
US Secretary of State Condoleezza Rice is due in Nairobi on Monday to help the peace effort led by ex-UN Secretary General Kofi Annan.
This is Mr Bush's second African trip, which will also take him to Rwanda, Ghana and Liberia.
Its main focus is on highlighting the success of projects to fight Aids and malaria.
HAVE YOUR SAY
Bush's visit is belated and unnecessary as it comes at the twilight of his administration
Ashipa James Olashupo, Abuja
Mr Bush urged the US Congress to renew his global programme to combat Aids. He also wants it doubled from $15bn to $30bn.
"We don't want people guessing on the continent of Africa whether the generosity of the American people will continue," he said in Dar Es Salaam.
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.
So far, Liberia is the only nation to have offered to host the US base. There are already some 1,700 US troops in Djibouti.
Mr Bush has also called for urgent action over the "genocide" in Sudan's region of Darfur, where at least 200,000 people have died and two million been displaced since 2003.
In a BBC interview prior to his tour, the US president defended his decision not to send soldiers to Darfur, saying he had not wanted to deploy US troops into another Muslim country.