A U.S. senator wants a top United Nations official out of office after two world leaders accused of human rights violations were invited to an international summit on food and hunger issues held this week in Rome.

Sen. Tom Coburn, R-Okla., said Wednesday that U.N. Food and Agriculture Organization Director General Jacques Diouf should resign for featuring at the summit Zimbabwe's embattled President Robert Mugabe, who made his first trip abroad since contested elections earlier this spring, and Iranian President Mahmoud Ahmadinejad, who has called for Israel's destruction, Both men drew rebukes from international leaders for their appearances.

"Diouf made a mockery of the 2008 World Food Summit," a statement from Coburn's office said, adding that Mugabe and Ahmadinejad "are responsible for the misery and starvation of millions."

If the FAO leader doesn't resign, Coburn wrote in letters to letters to Secretary of State Condoleezza Rice, Agriculture Secretary Ed Schafer and USAID Administrator Henrietta Fore, then U.S. funding for the organization -- some $100 million annually -- should be stripped of the program.

"Providing a U.S. taxpayer-funded forum for these men to present themselves as humanitarians is unconscionable," Coburn wrote in the letters.

Coburn also demanded to know how many people were sent by the Bush administration to Rome for the June 3-5 summit, as well as the amount of money being spent on the summit.

"On the face of it, this event does not sound like a good prioritization of taxpayer funds," Coburn wrote.

The FAO regional office in Washington, D.C., did not provide an immediate response to a request for comment by FOXNews.com.