The US national security adviser says an aircraft carrier task force and a squadron of airforce bombers are being deployed to the Middle East as a warning to Iran.
The move followed "clear indications" that Iranian and Iranian proxy forces were preparing to possibly attack US forces in the region, a defence official told the Associated Press.
US forces at sea and on land were thought to be the potential targets.
White House national security adviser John Bolton confirmed that the US was deploying the USS Abraham Lincoln Carrier Strike Group and a bomber task force to the US Central Command region, an area that includes the Middle East.
Mr Bolton said the move was in response to "a number of troubling and escalatory indications and warnings".
He did not provide details, but said the US wants to send a message that "unrelenting force" will meet any attack on US interests or those of its allies.
"The United States is not seeking war with the Iranian regime, but we are fully prepared to respond to any attack, whether by proxy, the Islamic Revolutionary Guard Corps, or regular Iranian forces".
The Abraham Lincoln and its strike group of ships and combat aircraft have been operating in the Mediterranean recently.
Mr Bolton's reference to the Central Command area would mean the Lincoln is headed east to the Red Sea and perhaps then to the Arabian Sea or the Persian Gulf.
The US Navy currently has no aircraft carrier in the Persian Gulf.
Mr Bolton's mention of deploying a bomber task force suggests the Pentagon is deploying land-based bomber aircraft somewhere in the region, perhaps on the Arabian Peninsula.
The Trump administration has been intensifying a pressure campaign against Iran.
Last month, President Donald Trump announced the US will no longer exempt any countries from US sanctions if they continue to buy Iranian oil, a decision that primarily affects the five remaining major importers: China and India, and US treaty allies Japan, South Korea and Turkey.
The US also recently designated Iran's Revolutionary Guard as a terrorist group, the first ever for an entire division of another government.