US President Donald Trump revealed to Axios that a US rescue mission for a downed F-15 pilot in Iran was nearly called off after American forces feared they were being lured into an Iranian trap.

The alarm was triggered by a radio transmission picked up by US intelligence, raising concerns it could be a deceptive signal designed to ambush US forces.

Trump said the weapons system officer gave a short, unusual message over his radio after ejecting from the aircraft. "He said: 'Power be to God.'"

"What he said on the radio sounded like something a Muslim would say," Trump said, referring to a message from the pilot saying "God is good."

Trump detailed that almost 200 special units soldiers participated in the operations, adding that "Israel" provided "a little bit" of help.