"It is time for Mugabe to go," said Ambassador James McGee. "He's outlived his usefulness in Zimbabwe."
The current humanitarian crisis in Zimbabwe -- including a cholera outbreak -- is linked to the political crisis, McGee said during a news briefing.
World Health Organization officials said the cholera outbreak resulted in the death of least 783 people have died and reported infections of more than 16,400 people.
"And this political crisis is nothing more than the result of the failed economic policies, corruption and human rights abuses on the part of the government of Zimbabwe," he said.
Global leaders, including U.S. President George Bush, have called upon Mugabe to step aside.
"And I think that what we're seeing right now with this ... man-made humanitarian crisis that they're absolutely correct," he said.
Meanwhile the U.S. Agency for International Development, which provides economic and humanitarian assistance, allocated $6.2 million in addition funds to help battle the cholera outbreak in Zimbabwe, officials said. The agency already given $4.6 million in help, providing emergency water, sanitation and hygiene programs, said Henrietta H. Ford, USAID administrator.
The agency already sent to Zimbabwe a disaster assistant response team of water and sanitation, public health and emergency experts from USAID as well as from the Centers for Disease Control and Prevention, Fore said.