Prime Minister Junichiro Koizumi argued Thursday that Iraqi President Saddam Hussein triggered the 2003 invasion of his country and Japan was justified in supporting the U.S.-led multinational force that launched the "pre-emptive" attack.

"If Iraq had proved it had no weapons of mass destruction, the war wouldn't have occurred," Koizumi told reporters at the Prime Minister's Official Residence in Tokyo. "I wonder why President Hussein hid (the facts and did) not listen to the United Nations."

Japan supported the U.S-led war against Iraq based on allegations made mainly by U.S. intelligence sources, most notably a Feb. 5, 2003, speech by then U.S. Secretary of State Colin Powell made to the U.N. Security Council.

Koizumi insisted Japan backed the war against Iraq based on the resolutions of the U.N. Security Council, instead of the allegations leveled by the U.S.

Koizumi's comments came a day after U.S. President George W. Bush accepted responsibility for the intelligence shortcomings on Iraq's alleged possession of weapons of mass destruction, which have not been found.

"It is true that much of the intelligence turned out to be wrong. As president, I'm responsible for the decision to go into Iraq," Bush said during a speech Wednesday.