The US is sending a Patriot missile-defence system to the Middle East amid escalating tensions with Iran.
A warship, USS Arlington, with amphibious vehicles and aircraft on board, will also join the USS Abraham Lincoln strike group in the Gulf.
And US B-52 bombers have arrived at a base in Qatar, the Pentagon said.
The US said the moves were a response to a possible threat to US forces in the region by Iran, without specifying. Iran dismissed the claim as nonsense.
Tehran has described the deployments as “psychological warfare” aimed at intimidating the country.
Iran has also suggested it may resume uranium enrichment nuclear activities.