The Japanese government on Friday approved a plan to allow the nation's troops to join a UN-sanctioned multinational force in Iraq after Iraq's interim government takes control at the end of June.

The plan also noted that the Self-Defense Forces (SDF) will not come under the force's unified command and will continue conventional activities at Japan's discretion.

Around 500 ground troops are deployed in the Iraqi southern city of Samawah to help with humanitarian and rebuilding efforts. They are supported by around the same number of air and maritime troops in Kuwait.

A special law passed last year authorized the largest overseas deployment since World War II. However, the SDF activities are under strict restrictions because the operation is sensitive considering Japan's pacifist constitution.

The law ruled that the troops shall operate only within noncombat areas and not use weapons except when life is under threat.

Japanese Prime Minister Junichiro Koizumi told US President George W. Bush at the just-concluded G-8 summit meeting that Japan would participate in the multinational forces endorsed by the United Nations after the Iraqi interim government takes power on June 30.

The opposition camp strongly contested the decision, arguing that it went against the constitution and without parliamentary discussion. However, the ruling parties maintained that the special law had authorized the cabinet to make decision without the approval of the parliament in the middle of the operation.

Koizumi vowed Tuesday to follow the principles such as confining activities in humanitarian assistance, restraining from exercising force, avoiding combat regions, and putting the troops under Tokyo's command.

"The Self-Defense Forces will continue their activities in Iraq within the framework of the special law for Iraqi assistance, and will remain under the command of Japan," he said.

He stressed that "Their activities will be restricted to humanitarian reconstruction efforts even if they join in the multinational force."

In the face of the upper house election on July 11, the Iraq issue has been strenuously targeted by the opposition camp. Katsuya Okada, president of the major opposition Democratic Party of Japan, reiterated the same day the demand to pull troops out of Iraq, calling voters to stay away from the ruling parties if they want changes in politics.