I was wrong over Iran plane cash: Trump

Donald Trump has tweeted that he was mistaken about his claim that he saw a video of a US cash payment going to Iran.

File image of Donald Trump Source: AAP

Donald Trump is making a rare admission he was wrong - in claiming he saw a video of a US cash payment going to Iran.

Trump tweeted on Friday that "The plane I saw on television was the hostage plane in Geneva, Switzerland, not the plane carrying $400 million in cash going to Iran!"

Trump has been expressing outrage about a $US400 million payment the US made to Iran this year.

It was delivered on the same day that Iran released four Americans they had detained. Republicans call it ransom; the Obama administration says it was money the US legally owed Iran.

Trump said on Wednesday he saw video showing the money being delivered.

The campaign acknowledged Thursday that this was incorrect, yet Trump repeated the claim hours later at a rally.