The United States will move a Patriot air defence missile system into the Middle East to counter threats from Iran.

The Pentagon announced the move following concerns that Tehran may be planning an attack on American forces or interests in the region.

An official said the decision comes after intelligence showed that the Iranians have loaded military equipment and missiles on to small boats controlled by Iran's Revolutionary Guard.

The Pentagon has also said that the USS Arlington, an amphibious transport ship, will move to the Middle East region earlier than planned.

The ship is in Europe and will be replacing the USS McHenry, which is scheduled to leave.

Advertisement Earlier this week, officials said that sending a Patriot missile defence system to the area was under discussion and was part of the initial request made by the Pentagon's US Central Command.

They said it took a few days to get final approval for the Patriot, a long-range air defence system to counter tactical ballistic missiles, cruise missiles and advanced aircraft.

More from United States US-China trade war: How did it start and what does it all mean? China 'tired' of hearing US criticism on Belt and Road plans Magic mushrooms decriminalised in Denver Chinese spies 'used US hacking tools a year before Russians leaked them online' Global markets slide after Trump issues new tariff threat US warns Iran of 'unrelenting force' as it sends USS Abraham Lincoln to Gulf The US removed Patriot systems from Bahrain, Kuwait and Jordan last year. It was not clear if the system would go back to one of those countries.

On Sunday US officials announced that they would rush an aircraft carrier strike group and bombers to the region.

The aircraft carrier USS Abraham Lincoln and accompanying ships have passed through the Suez Canal and are now in the Red Sea.

Officials had initially indicated that the military moves were based in part on indications that Iran had moved short-range ballistic missiles on to small boats called dhows along its shore.

They would not say if the intelligence showed that the boats have mobile launchers on them, but a notice to mariners in the region has warned of potential threats to commercial maritime traffic.

US national security adviser John Bolton announced the initial moves, citing "troubling and escalatory indications and warnings" but did not explain what they were.