Iran's foreign ministry spokesman Abbas Mousavi. (AFP)

Iran strongly rejected an accusation by US National Security Advisor John Bolton on Wednesday that it was "almost certainly" behind May 12 attacks on four ships off the United Arab Emirates.

"Making such laughable claims... is not strange" coming from the US, foreign ministry spokesman Abbas Mousavi said in a statement on its official website.

"Mr Bolton and other warmongers and chaos seekers should know that the strategic patience, high vigilance and complete defensive readiness of the Islamic Republic of Iran... will prevent the fulfilment of their evil desires for chaos in the region," Mousavi added.

Bolton made his accusation that the four ships were hit by "naval mines almost certainly from Iran" while in the UAE capital Abu Dhabi to discuss what he says is the threat from Tehran.

"There's no doubt in anybody's mind in Washington who's responsible for this," Bolton said in a clear reference to Iran.

The accusation comes amid a US military buildup in the Gulf and on the eve of emergency Arab and Gulf summits called by Iran's regional rival Saudi Arabia to discuss the standoff.

It also comes two days after President Donald Trump struck a dovish tone during a visit to Japan saying that Washington was not seeking "regime change" in Iran and was open to talks.

Bolton said US reinforcements were sent to the region as a "deterrent" and Washington's response would be prudent.