Japanese Defense Minister Satoshi Morimoto said Friday his country is awaiting the outcome of investigations into recent crashes of two V-22 Ospreys before it will sign off on allowing U.S. Marines to operate the aircraft on Okinawa.

Morimoto said Japan will work closely with the United States in reaching any decision about operations for the dozen V-22s that arrived in July. The Marines were allowed to deploy the V-22s but under the condition that they not engage in operations until inquiries into the accidents were completed and Tokyo is satisfied they are safe to fly.

“The United States will give us the report of the investigations with regard to what happened in Florida and Morocco as soon as possible, and until we confirm the safety of it the United States will refrain from flying the Osprey,“ Morimoto said through a translator at a Pentagon press conference with his U.S. counterpart, Leon Panetta.

Panetta said he expects the study on the accident to be complete within a month and presented to the Japanese government and in the meantime the Marines will refrain from flying the V-22 based on Okinawa in the “short term.”

Panetta said the V-22s are crucial for extending the reach and response time of Marines in the Asia-Pacific region, from anything from military contingencies to disaster relief. Panetta said the tilt-rotor aircraft has proven to be safe.

“The Osprey is a critical aircraft,” Panetta said.

Okinawa residents, historically weary of the Marine presence on the island, are worried the Ospreys pose a safety hazard, and that concern grew after an April crash of a Marine Corps version, the MV-22, in Morocco that killed two Marines. That was followed by an accident in Florida involving an Air Force version known as the CV-22. Four people were injured.

The Pentagon has staunchly defended the safety record of the aircraft that have been deployed to Iraq and Afghanistan, and other countries. Ospreys can occasionally be seen in the skies above Washington.

The aircraft are built by a partnership between Boeing [BA] and Bell Helicopter, a unit of Textron [TXT].

The image of the aircraft has continued to be plagued by problems dating to its development in the 1990s that involved several fatal accidents and caused the program to be put on hold. The Pentagon has since maintained that the problems were worked out and the Ospreys are now among the safest in the U.S. fleet.

Morimoto was to fly in a V-22 following the press conference.