Australia is committed to buying a total of 72 F-35 Joint Strike Fighters, the Pentagon’s most expensive weapons system, Defense Minister David Johnston said.

The U.S. ally is ordering 58 of the Lockheed Martin Corp.- made aircraft, on top of the 14 it pledged to buy in 2009, Johnston told reporters in Canberra today, without giving further details. The Australian Financial Review reported the additional order will cost A$12.4 billion ($11.6 billion), citing a copy of a speech Prime Minister Tony Abbott is scheduled to deliver today.

“There’s nothing else on the market that has the capability, the capacity, the cutting-edge technology that this brings to the game,” Johnston said.

Pentagon estimates released April 17 show the projected cost to develop and produce the F-35 fighter has risen 1.9 percent in the past year to $398.6 billion. Original international partners such as Italy, Turkey and Canada have indicated they are re-evaluating their purchase plans, while Israel, Singapore, Japan and South Korea are being monitored for signs their procurement orders may be affected by rising costs.

The projected acquisition cost of the F-35 has climbed 71 percent in inflation-adjusted dollars since the Pentagon signed its initial contract with Lockheed in 2001, even as plans were adjusted to buy 409 fewer aircraft. Congress has approved spending $83.2 billion on the F-35 so far.

The project has also been beset by technical troubles, such as jittery images in the pilot’s helmet. The Pentagon has questioned the progress of the plane, finding in January that the fighter wasn’t sufficiently reliable in training flights last year and developed cracks in ground testing.

Abbott, whose Liberal-National coalition was elected in September, needs to balance Australia’s interests between strategic ally the U.S. — which has as many as 2,500 Marines based in the northern city of Darwin — and top trading partner China, which it criticized last year for creating an East China Sea air defense identification zone.