The top U.S. Marine Corps commander has lauded the first joint drill involving a Maritime Self-Defense Force ship and tilt-rotor Osprey aircraft, such as those deployed to Japan.

"It was pretty monumental," Gen. James Amos, commandant of the U.S. Marine Corps, told reporters Wednesday in Washington, referring to a recent drill in California in which an MV-22 Osprey landed on the MSDF ship.

"It turned out to be an incredible amphibious exercise," Amos said of the drill, which was part of a series of exercises involving the United States, Japan, Canada and New Zealand.

The Dawn Blitz exercises that began earlier this month are aimed at enhancing the amphibious capabilities of the participating militaries.

Amos also said cooperation between the U.S. Marine Corps and the Self-Defense Forces has been strengthened through joint disaster-relief operations following the mega-earthquake and tsunami that hit northeastern Japan in March 2011.

"I'm continuing with the new marine orientation to the Pacific, including exercises in Japan," he said.

The deployment of the hybrid aircraft to U.S. Marine Corps Air Station Futenma in a densely populated area of Okinawa last October has stirred controversy, amid concerns about the aircraft's safety following a fatal crash in Morocco and another crash in Florida, both earlier that year.