Tokyo has secured cost cuts on support equipment for its next batch of six U.S. F-35 stealth fighter aircraft of around $100 million, according to sources and Japanese budget papers, on top of savings being finalized for all buyers of the high-tech jets.

The deal represents a rare case of Tokyo talking down the price of military hardware from its U.S. ally and underscores progress for the Lockheed Martin Corp.-run F-35 program, which has faced criticism for cost overruns and other problems.

U.S. President Donald Trump, who called the program as "out of control" in December, said on Monday he had been able to shave some $600 million from the latest U.S. deal to buy about 90 F-35s from Lockheed.