Japan moved ahead Friday with its plan to send two navy ships to the Somali coast to join an international anti-piracy mission, despite criticism the step may draw troops into action that goes beyond its pacifist constitution.

Defense Minister Yasukazu Hamada, following Cabinet approval earlier in the day, ordered the two warships to leave for Somalia's waters Saturday to protect Japanese vessels and crews from pirates. The destroyers, carrying about 400 sailors and eight coast guard officials, will leave Japan's southwestern port of Kure.

"Piracy is a threat to the international society, including Japan, and is a problem that must be dealt with urgently," Hamada told reporters. "The government bears a serious responsibility to protect the lives and assets of our people in the waters."

Japan's dispatch marks the first policing action overseas for Japan's military, whose mission has been largely restricted to refueling, airlifting and other humanitarian activities.

Opposition lawmakers say Japanese ships could be pressed into combat or protecting foreign ships in an emergency.

The post-World War II charter limits Japan's military to defensive operations. Its naval ships can only be deployed to protect Japanese boats and their crews. Ruling party members have argued that the battle against piracy is more a crime-fighting operation than a military one.

Japan's dispatch comes as more than a dozen warships from countries including Britain, the United States, France and Germany are guarding the region.

The two Japanese destroyers, Sazanami and Samidare, which are also carrying two SH-60K patrol helicopters and a pair of speedboats, are expected to reach Somali waters in early April.

Somalia, without a functioning government since warlords overthrew a dictator in 1991, has failed to protect citizens while it battles a growing Islamist insurgency.