The US Department of Defense says there has been no official request from Japan to ground Osprey transport aircraft, following Wednesday's crash into the sea of a CV-22 Osprey in southwestern Japan.

Japan's Defense Minister Kihara Minoru said on Thursday that he had met the top official of the US military in Japan and asked him to suspend flights of all Japan-based US Osprey aircraft, except for search and rescue missions, until their safety is confirmed.

Deputy Pentagon Press Secretary Sabrina Singh said at a regular news conference on Thursday that she was not aware of any official request for a suspension.

She said, "As of right now, we are still continuing to operate the Osprey aircraft."

She added that if the ongoing investigation should yield any results that require the department to take additional steps, the US military will certainly do that.