Baghdad ? Iraqi Prime Minister Nouri al-Maliki on Sunday ordered a “professional and neutral” investigation into the violence that killed more than 50 people at a religious festival last week.

Speaking at a news conference in Baghdad’s heavily fortified Green Zone, Maliki also strongly rebuked U.S. congressional Democrats who have called for his ouster.

“They do not realize the size of the disaster that Iraq has passed through and the major role of this government, a government of national unity,” Maliki said in response to a question about calls for his removal from a handful of U.S. senators. “The most important achievement is it stopped a sectarian and civil war.”

In less than two weeks, the White House is scheduled to receive a report about conditions in Iraq seven months into a stepped-up security plan that sent 30,000 additional troops to Baghdad. Last month, Sens. Hillary Rodham Clinton, D-N.Y., Carl Levin, D-Mich., and John Warner, R-Va., said that Maliki should be replaced because of his inability to unify rival political factions. Nearly half of Maliki’s Cabinet is boycotting meetings, and the government has made little visible progress on a series of political benchmarks considered key by the Bush administration.