Japanese Defense Minister Takeshi Iwaya and acting U.S. Defense Secretary Patrick Shanahan agreed Friday to step up cooperation both in the search for an F-35A fighter that crashed off Aomori Prefecture and in the investigation into the cause of the accident.

Iwaya and Shanahan reached the agreement in a meeting at the Pentagon. Both countries are concerned about the implications of the next-generation aircraft being recovered by a rival like China or Russia as it could constitute a major military intelligence security breach.

Speaking to reporters after the meeting, Iwaya said Shanahan told him that the United States will dispatch a deep-sea search ship to the crash site in a joint effort with Japan's Maritime Self-Defense Force to recover the bulk of the wreckage of the Lockheed Martin-designed aircraft.

(L-R) Japan's Defense Minister Takeshi Iwaya, Foreign Minister Taro Kono, U.S. Secretary of State Mike Pompeo and Defense Secretary Patrick Shanahan

The plane went down on April 9 in the Pacific Ocean off the northeastern Japanese prefecture during a Japanese Air Self-Defense Force exercise. The pilot of the single-seat stealth jet remains missing.

Asked by a reporter about the possibility of China retrieving the crashed aircraft, Iwaya said, "We are continuing search activities under strict surveillance. I don't see such a possibility."

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Despite the crash, Iwaya said Japan will proceed with planned F-35A fighter purchases from the United States.

"At this point, we have no specific information that would lead to a change in our procurement plan," he said. "We have no plan to alter the acquisition and deployment plan."

The Japanese minister also said he demanded the United States take measures to prevent the recurrence of incidents like the recent death of a U.S. serviceman and a Japanese woman in Okinawa Prefecture.

Iwaya said it is "extremely regrettable" that such an incident occurred when the two governments are promoting the realignment of American troops in Japan, including a planned relocation of U.S. Marine Corps Air Station Futenma within the southern island prefecture that hosts the bulk of U.S. military facilities in the country.

The serviceman and the woman were found dead April 13 at an apartment in the town of Chatan. U.S. military sources have said the man may have killed the woman and then committed suicide.

Shanahan apologized for the incident, saying it was a painful and regrettable case.

Iwaya and Shanahan reaffirmed that relocating Futenma from a crowded residential area in Ginowan to the less-populated coastal district of Henoko in Nago is the "only solution" to avoid the safety and noise concerns that have plagued the base.

(File photo taken on May 28, 2018 shows the F-35A fighter jet that crashed into the Pacific Ocean on April 9 during a training exercise)