MOSCOW — Russia is sending a reconnaissance ship to the eastern Mediterranean, Interfax news agency reported on Monday, as the United States prepares for a possible military strike in Syria.

The reconnaissance ship Priazovye left Russia's naval base in the Ukrainian Black Sea port of Sevastopol late on Sunday on a mission "to gather current information in the area of the escalating conflict," the report quoted an unidentified military source as saying.

The Defense Ministry declined immediate comment.

President Barack Obama said on Saturday he would seek congressional authorization for punitive military action against Syrian President Bashar Assad after what the United States says was a sarin gas attack that killed more than 1,400 people.

Russia says the United States has not proved its case, and that it believes the attack was staged by rebels to provoke intervention in the more than two-year-old civil war.

Russia is one of Assad's biggest arms suppliers and has a naval maintenance facility in the Syrian port of Tartous. Moscow opposes any military intervention in Syria and has shielded Damascus from pressure at the U.N. Security Council.

Interfax said the Priazovye would be operating separately from a navy unit permanently stationed in the Mediterranean in a deployment which President Vladimir Putin said is needed to protect national security interests.

The Defense Ministry said last week that new warships would be sent to the Mediterranean to replace others in a long-planned rotation of the ships based there.