TOKYO - Japanese lawmakers on Wednesday approved a two-year extension of the country's air force transport mission in Iraq, despite criticism of Tokyo's involvement in the increasingly unpopular war.

The legislation cleared the upper house with support from members of Prime Minister Shinzo Abe's ruling Liberal Democratic Party and its coalition partner, the New Komei Party, upper house official Yuji Masaki said.

The lower house -- also dominated by the ruling coalition -- approved the legislation last month.

The government has argued that the mission is needed to help stabilize Iraq and prevent the spread of terrorism.

Japan backed the U.S.-led Iraq invasion and provided troops for a 2004-2006 non-combat, humanitarian mission in southern Iraq. Last year it expanded its Kuwait-based operations to airlift U.N. and coalition personnel and supplies into Baghdad.

The approval could give a boost to Abe as he tries to raise Japan's military profile internationally.

Abe has sought to change the country's pacifist constitution to allow Japan's military greater freedom to join peacekeeping missions and possibly come to the aid of an ally under attack.

The Iraq mission is part of that attempted shift to a more assertive foreign policy. Still, some Japanese say any overseas military operations violate the spirit of the post-World War II constitution, which prohibits using force to settle international disputes.

The public has also increasingly criticized U.S. policy in Iraq, while critics warn Tokyo's support of Washington has made Japan a terrorist target.