Republican presidential candidate Donald Trump told supporters at a rally in Pensacola, Florida on 13 January, that the reason US sailors were detained and later released by Iran was "money".

Iran freed 10 US sailors a day after detaining them aboard two US Navy patrol boats in the Gulf, bringing a swift end to an incident that had rattled nerves just before the expected implementation of a landmark nuclear accord. There were no indications the sailors were harmed while in Iranian custody, the Pentagon said.

Republican presidential candidates are critical of the nuclear deal Iran forged with six world powers and due to take effect soon. Trump, who accuses President Barack Obama of being weak on foreign policy, slammed the treatment of the American sailors.

"You saw those poor guys today at the boat, the way that guy was shouting at him, that thug," Trump said.

"I told you before, we only got them back because they haven't gotten their money, if this would have taken place two weeks from now we wouldn't have got them back," Trump added, in reference to the money promised to be given back to Iran as part of the P5+1 deal that was signed under the leadership of the Obama administration.

Trump also expressed his frustration with the audio quality of his microphone and vowed not to pay the person who installed it during the campaign rally. He went as far as to use expletives to describe the person who may have been responsible for his microphone, which was making a "popping" noise.

"By the way, I don't like this mic. Whoever the hell bought this mic system, don't pay the son-of-a-b**ch that put it in," Trump said.

"Don't pay 'em. You know, I believe in paying, but when somebody does a bad job, like this stupid mic, you shouldn't pay the bastard. Terrible."