Takenori Kanzaki, leader of New Komeito and a key coalition ally of Prime Minister Junichiro Koizumi, left for Kuwait on Tuesday and may visit southeastern Iraq if circumstances permit.
Chief Cabinet Secretary Yasuo Fukuda told a news conference that Kanzaki had not consulted people in the government or the ruling Liberal Democratic Party about the trip.
Koizumi told reporters later in the day he did not know about the trip, prompting some in political circles to describe the move as controversial.