The US has moved a Patriot air defence missile system into the Middle East to counter threats from Iran, the Pentagon has said.
The move reflects ongoing concerns that Tehran may be planning to attack America forces or interests in the region.
A US Defence Department official said the decision came after intelligence showed that the Iranians have loaded military equipment and missiles on to small boats controlled by Iran’s Revolutionary Guard.
Officials had said earlier this week 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, all-weather air defence system to counter tactical ballistic missiles, cruise missiles and advanced aircraft.
The US removed Patriot systems from Bahrain, Kuwait and Jordan late last year. It was not clear if the system would go back to one of those countries.
ITV News Correspondent Rebecca Barry reports on growing tensions between Washington and Tehran
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.
Officials 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.
John Bolton, the national security adviser, announced the initial moves on Sunday, citing “troubling and escalatory indications and warnings” but did not explain what they were.
On Friday, a defence official said the Iranian threats also include potential attacks by Iranian proxies, such as Shia militias in Iraq.
Several officials said they have not yet seen any tangible move by Iran in reaction to the US military shifts in the area. But they also noted there have been no attacks.
US Secretary of State Mike Pompeo made a quick visit on Tuesday to Baghdad to meet with top leaders and underscore Iraq’s need to protect Americans in their country.
The Pentagon also said on Friday 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.