Iran has sent two warships to the Gulf of Aden, off the coast of Yemen, where the United States conducted missile attacks.
The announcement came after the U.S. military launched cruise-missile strikes to knock out radar sites in Yemen controlled by Iran-allied Huthi forces, after failed missile attacks this week on a U.S. Navy destroyer.
"Iran's Alvand and Bushehr warships have been dispatched to the Gulf of Aden to protect trade vessels from piracy," the semiofficial Tasnim news agency reported on October 13.
But Tasnim said the two Iranian destroyers were dispatched on October 5 and it was not in response to U.S. actions in Yemen.
Tasnim said the Iranian warships will patrol the Gulf of Aden, south of Yemen, which is one of the world's most important shipping routes.
The strikes on October 13, authorized by U.S. President Barack Obama, were Washington's first direct military action against Huthi targets in the Yemen civil war, although the United States has provided logistical support to the Saudi-led coalition battling the rebels.
The Pentagon stressed that the strikes were defensive and aimed at radar that enabled the launch of three missiles this week against the U.S. Navy destroyer USS Mason.
"These limited self-defense strikes were conducted to protect our personnel, our ships, and our freedom of navigation," Pentagon spokesman Peter Cook said.
"The United States will respond to any further threat to our ships and commercial traffic, as appropriate."
Huthi rebels deny they have targeted any warships.
A Saudi-led coalition is carrying out an air campaign against the Huthi rebels.
U.S. support for the coalition has come under strain following an air strike on a funeral in Sanaa last weekend that killed 140 people.
Iran's key regional rival, Saudi Arabia, accuses Tehran of providing support to the Huthis, a charge Tehran denies.