Opposition parties on Tuesday slammed Prime Minister Junichiro Koizumi's emphatic support for the United States' ultimatum to Iraq, saying a peaceful solution to the crisis should be achieved through more U.N. inspections.

Naoto Kan, leader of the Democratic Party of Japan, said Koizumi has failed to provide a convincing explanation for why he supports a U.S military attack on Iraq in the absence of a new U.N. resolution.

He also pointed out the suddenness with which the government has begun to argue that previous U.N. resolutions provide sufficient cover for the U.S. to wage war against the regime of Saddam Hussein.