As the U.S. moves ships and planes into the eastern Mediterranean for a threatened attack on Syria, Iran has announced that a new destroyer will join its fleet, a state-run news agency reported Sunday.

The timing seems designed to counter the U.S. threat, which Iran has denounced. Iran has a huge stake in the survival of President Bashar al-Assad’s regime as its main Arab allies are Syria and its proxy Hezbollah, the Lebanese Shi'ite army that is fighting alongside Assad to quell Sunni-dominated rebel forces.

A sixth US Navy warship has joined five U.S. destroyers armed with cruise missiles in the eastern Mediterranean Sea. as a precautionary measure.

Meanwhile, a U.S. official Tuesday told ABC News that four ships including the carrier USS Nimitz have moved into the Red Sea. The carrier strike group entered the Red Sea to move resources to “maximize available options," the Navy said.

The carrier was redeployed after it ended a months-long deployment in the Arabian Sea supporting the war in Afghanistan and was replaced with the USS Harry S. Truman. The Nimitz was heading west back to its home port in Everett, Wash., when it received orders to turn back to the region.

The increase in U.S. naval forces in the Mediterranean comes as Russia last week announced that it was sending two ships to the eastern Mediterranean, an anti-submarine vessel and a missile cruiser.

The Russian navy denied that the deployment was linked to the events in Syria.

Russia also has a stake in Syria as Assad is his only regional ally. Russia also has one of its last foreign naval bases in Tartus, Syria.

Russia’s interests in protecting Syria from Western forces are both economic and strategic. Also, Syria is one of Russia’s main remaining customers for arms.

The last major engagement involving Iran’s and U.S’s navy was on April 14, 1988, when the U.S. launched Operation Praying Mantis, after a guided missile frigate, the USS Samuel B. Roberts, struck an Iranian mine in the Persian Gulf.

In response the U.S. Navy attacked two Iranian oil platforms and destroyed 25 percent of the Iranian navy.