The US is sending a Patriot air defence missile system and a warship to the Middle East amid escalating tensions with Iran.
The USS Arlington, which transports amphibious vehicles and aircraft, will join the USS Abraham Lincoln strike group in the Gulf, officials say.
US B-52 bombers have also arrived at a base in Qatar, the Pentagon said.
It said the moves were a response to threats of possible operations against US forces in the region by Iran.
The US has given little information about the exact nature of the reported threat, which Iran has dismissed as nonsense. Tehran has described the deployments as “psychological warfare” aimed at intimidating the country.
Meanwhile Iran’s semi-official Isna news agency quoted a senior Iranian cleric, Yousef Tabatabai-Nejad, as saying that the US military fleet could be “destroyed with one missile”.
On Friday, the Pentagon said that the US did not seek conflict with Iran, but that Washington was “ready to defend US forces and interests in the region”.
“The Department of Defense continues to closely monitor the activities of the Iranian regime,” it said in a statement.
It added that the Patriot system – which it said could counter ballistic missiles, cruise missiles and advanced aircraft – was also being deployed in the event of any possible attack.
The USS Abraham Lincoln passed through the Suez Canal on Thursday, US Central Command said.
The BBC’s defence and diplomatic correspondent Jonathan Marcus says that while it is not unusual for an aircraft carrier and its battle group to be sent to the Gulf, the move will spark fears that a possible conflict could erupt either by accident or by design.
What’s the state of US-Iran relations?
Last year, US President Donald Trump unilaterally withdrew from a landmark nuclear deal America and other nations had agreed with Iran in 2015.
And last month the White House said it would end exemptions from sanctions for five countries – China, India, Japan, South Korea and Turkey – that were still buying Iranian oil.