MELBOURNE, Australia — Japan’s Ministry of Defense has confirmed it is seeking to increase it fleet of Boeing KC-46A Pegasus tankers, adding to its current order of four aircraft.

In response to queries from Defense News, a spokeswoman from the ministry said a budget request for four more KC-46s over the next fiscal year will bring its fleet to six aircraft. Japan already has two KC-46s on contract as part of an original 2015 request for four tankers under the U.S. government’s Foreign Military Sales program.

The latest Japanese budget request, released Friday, contained a line item asking for a further $1.05 billion to fund four more KC-46s, which will be for the remaining two aircraft from the 2015 order and another two.

Japan already awarded contracts to Boeing for two KC-46As previously on order, with contracts each for one aircraft worth $279 million and $159 million issued in December 2017 and 2018 respectively. The first contract included additional logistics support, which accounts for the higher cost.

The request for funding for four KC-46As is a departure from normal procedure. Japan tended to place such orders under a rolling acquisition system, with small numbers of aircraft or systems on a year-on year basis. According to the budget request document, the batch order is a more cost-effective means of acquisition, resulting in $100 million worth of savings.

The addition of the KC-46s will significantly enhance the aerial refueling capabilities of the Japan Air Self-Defense Force, of JASDF, which operates four Boeing KC-767 tankers at Komaki Air Base near the city of Nagoya, west of Japan’s capital Tokyo.

The KC-46s will be incorporated into a new JASDF unit and will also be used in a transport role.

The tankers will be compatible with the JASDF’s existing F-15J/DJ Eagle fighter jets, most of which are set to undergo an upgrade to improve electronic warfare and multirole capabilities.

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The tankers will also complement the Lockheed Martin F-35A/B Lighting II Joint Strike Fighters. Japan has ordered 157 F-35 jets, including 42 "B" models, which have less of an endurance than the "A" model because of the former’s short-takeoff-and-vertical-landing capability.

The Japanese government is placing more emphasis on the defense of remote southwest islands such as the Senkaku group, situated in the East China Sea approximately 550 miles from the Japanese mainland and whose ownership is disputed by China.