Opposition to the plan to temporarily base the helicopter-like planes in the city of Iwakuni has been rising since the fatal crash in April left two Marines dead in Morocco.
Japan's defense minister said Tuesday he may go to the city of Iwakuni to persuade local officials to accept the temporary deployment. But after meeting with ministry officials on Monday Iwakuni's mayor said he needs more assurances that the aircraft is safe.
The U.S. military wants to replace aging helicopters on the island of Okinawa with the Osprey after bringing them to Iwakuni for about two weeks later this year for assembly and testing. Local approval is not essential for the project to go ahead, but Japan's central government prefers to have the support of local officials.
The $70 million Osprey is the U.S. military's latest-generation transport aircraft.
It combines airplane-like wings with rotors that allow it to take off and land like a helicopter. Its engines roll forward in flight, allowing it to fly faster than a standard helicopter.
The Osprey program was nearly scrapped after a history of mechanical failures and two test crashes that killed 23 Marines in 2000. But development continued, and the aircraft have been deployed to Iraq.
While the General Accounting Office questioned the Osprey's performance in a report last year, the Marine Corps has called it effective.
An Air Force version of the aircraft crashed in Afghanistan in April 2010, killing three service members and one civilian contractor.
The United States has about 50,000 troops based throughout Japan, with most of them on Okinawa.
Opponents of the bases often complain of the danger of accidents involving local residents, and some have complained about the impending arrival of the Osprey. The Associated Press