WASHINGTON - Every one of the more than 825 F-35 fighter jets delivered so far contain a component made with a Chinese alloy that's prohibited by both US law and Pentagon regulations, according to the programme office that oversees the aircraft.

The component - a magnet used in an aircraft-powering device supplied by Honeywell International - has been used in the plane since 2003, the Pentagon's F-35 program office said.

On Wednesday, the Pentagon suspended deliveries of new F-35s to make sure the programme complies with regulations related to "specialty metals."

The F-35 program - which may result in over 3,300 jets - will now seek a national security waiver from the Pentagon's top acquisition official to resume deliveries of already assembled new aircraft containing the alloy, F-35 spokesman Russell Goemaere said.

The program office does not anticipate "replacing magnets in delivered aircraft," he said.

Replacing them could entail costly and time-consuming retrofits of the over 500 US training and operational aircraft.

The Pentagon and Lockheed Martin, which builds the aircraft, have found a US source for the alloy for future planes, the company said.

"Further investigation is under way to understand the causal factors for the non-compliance and to establish corrective action," Goemaere said.

US law and Pentagon acquisition regulations prohibit the use of specialty metals or alloys made China, Iran, North Korea or Russia. The Defence Contract Management Agency reported the violation to the F-35 programme office on Aug 19.

A decade ago, the Pentagon granted a waiver to Honeywell to use Chinese magnets in other F-35 components, saying the programme, already beset by delays and cost overruns, would have been slowed even more.

The part has no technical flaw and it poses no security risk to the US's top stealth fighter or its eight million lines of software code.

Rather, it's a question of supply-chain security and why the banned alloy was not detected by Honeywell.