Less than a month after the crash of an MV-22 Osprey off Okinawa, the Defense Ministry on Thursday gave a tacit nod to the U.S. military's planned resumption of in-flight refueling drills set to start Friday.

With the cause of the Dec. 13 accident still not fully disclosed, the U.S. move is sure to deepen anger among Okinawa residents.

The Defense Ministry said the U.S. military will resume aerial refueling exercises on Friday, and expressed "understanding" over the decision by the U.S. military.