Any mistake by the United States in the Gulf will be met with a firm response, Iran's Islamic Revolutionary Guard Corps Navy (IRGCN) said in a statement published on the Guard's news site Sepah News.

"We advise the Americans to follow international regulations and maritime protocols in the Persian Gulf and the Gulf of Oman and to refrain from any adventurism and false and fake stories," Sunday's statement from the IRGCN said.

Last week, the US military said 11 small fast boats of the IRGCN came very close to its Navy and Coast Guard ships in the Gulf, near Kuwait, calling the moves "dangerous and provocative".

The Revolutionary Guard acknowledged the incident, saying that the US sparked the tense encounter, without providing additional details.

At one point, US military said in a statement last week, the Iranian vessels came within nine metres of the US Coast Guard cutter Maui.

The US ships issued several warnings through bridge-to-bridge radio, blasts from the ships' horns and long-range acoustic noise-maker devices.

The Iranian ships left after about an hour, the US statement said.

The IRGCN said on Sunday, however, that its forces were conducting a drill when they were met by "provocative actions of the United States and their indifference to warnings”.

The Iranian statement added that the Americans later withdrew.

"They should be assured that the Revolutionary Guards navy and the powerful armed forces of the Islamic Republic of Iran see the dangerous actions of foreigners in the region as a threat to national security and its red line, and any error in calculation on their part will receive a decisive response."