Amid persistent local worries and community protests about the safety of the aircraft, Defense Secretary Chuck Hagel and his Japanese counterpart Itsunori Onodera said 12 more aircraft will be sent there this summer.
The two defense chiefs made the announcement at a joint press conference after a Pentagon meeting Monday on a range of issues.
The Japanese government approved the deployment of 12 Ospreys last fall after receiving additional security assurances from the Pentagon.
Okinawans were concerned about two Osprey crashes last year, in Florida and Morocco, particularly because the Okinawa base in in a residential area.