Washington DC - President Donald Trump on Monday threatened to jail journalists who reported a second crew member of a US F-15 fighter jet was missing after being shot down over Iran.

Trump told reporters that his administration was working to identify the "leaker" who revealed information about the crew member to the media.

"They basically said that 'we have one and there's somebody missing.' Well, they didn't know there was somebody missing until this leaker gave the information," he said.

The fighter jet was shot down over Iran on Friday, sparking major concern in Washington that Iranian forces might capture the two crew members and use them as leverage in negotiations to end the fighting.

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The pilot was rescued shortly after the aircraft crashed, with US special forces subsequently deployed to prevent the capture of the second crew member, who has since been recovered.

Trump claimed the disclosure of the pilot's rescue made it clear to Iranian forces that the second crew member was still missing, which he said complicated the rescue effort.

"So whoever it was, we think we'll be able to find it out because we're going to go to the media company that released it, and we're going to say, 'national security, give it up or go to jail.'"

Trump did not name the media organization or the journalist he was referring to.

In his second term, the 79-year-old has massively ramped up attacks of press freedom and has frequently called for repression of dissent and critical coverage.