MELBOURNE, Australia — Norwegian company Kongsberg Defence & Aerospace has entered into a contract with Japan to supply the initial deliveries of Joint Strike Missiles for the country’s fleet of F-35 Lightning II fighter jets.

“This is a major milestone for the JSM program, entering into the production phase,” said Eirik Lie, the president of Kongsberg Defence & Aerospace, adding that the company was “very proud to have been selected by Japan to provide the JSM for their F-35 fleet.”

Neither Kongsberg nor Japan disclosed the dollar value or the number of missiles covered by the contract. However, Japanese budget documents show the country allocated 7.3 billion yen (U.S. $65.6 million) for the missile acquisition for the coming Japanese fiscal year, which begins March 31.

This almost certainly represents the cost of a small initial buy, and funding for more missiles will likely only appear during future budget cycles, especially given the JSM is only slated for integration on the F-35A during the Block 4 software release expected in the early 2020s.

Earlier checks confirmed that two JSMs can fit in the internal weapons bay of the F-35A, although the short-takeoff-and-vertical-landing F-35B can only carry the missile on its external weapons stations.

Japan plans to eventually acquire a total of 157 F-35s, which will include 42 F-35Bs. The east Asian nation will stand up its first squadron of F-35As later this year, and the Japan Air Self-Defense Force is currently training a cadre of flight and ground crews, as well as taking delivery of aircraft.

According to Kongsberg, the JSM is the only long-range missile that can be used against ship and land targets and also be carried internally in the F-35, the latter feature enabling the jet to maintain its stealthy, low-observable capabilities.

The JSM is based on Kongsberg’s land- and ship-launched Naval Strike Missile, which was primarily intended to be an anti-ship missile.

The company says the JSM adds standoff land-attack capability features such as low observability, agility and flexibility. An imaging infrared target seeker is used to identify a target. The missile has a range of up to 300 nautical miles in a high-high-low flight profile.

In 2015, Australia, which also wants to acquire the JSM for its own F-35s, signed an agreement to finance the development of a passive radio frequency seeker to complement the existing infrared target seeker.