More than 4,000 U.S. Marines and sailors have arrived in Japan to help with earthquake relief.

The 31st Marine Expeditionary Unit and Amphibious Squadron 11 arrived this morning off the west coast of Honshu, the MEU reports. The amphibious ship USS Harpers Ferry was scheduled to dock at Akita and prepare to unload equipment and personnel. The USS Essex, an amphibious assault ship, and USS Germantown, an amphibious dock landing ship, will remain at sea.

The expeditionary unit has 20 aircraft and 150 vehicles.

"If approved for operations, the 31st MEU is ready to rapidly send vehicles and aircraft east toward the affected areas," said operations officer Lt. Col. Michael Monti. "We can move water production capabilities to areas where there are water shortages, heavy equipment for debris removal, medical personnel to treat the wounded, and many other capabilities to help those in dire need."

The west coast of the main island "affords greater access to undamaged ports and roads, fewer navigational hazards and prevailing winds that are upwind of the Fukushima power plant," the MEU says.

The Pentagon said about 17,000 U.S. military personnel are involved in the relief operations.