The Pentagon said on Tuesday the Russian military was preparing to dispatch three ships to Syria but noted that Moscow's stated intent was to send supplies and personnel to its naval facility in the Mediterranean port of Tartus.
"We have no indication that these vessels and that material is being sent to Syria for any other purpose than that which the Russian military has acknowledged themselves," Pentagon spokesman Navy Captain John Kirby said.
"Russian citizens have been threatened there in Syria, and their stated intention is that this is for force protection reasons."
Kirby said the ships were separate from a cargo ship off the British coast that grabbed headlines on Tuesday. That ship, believed to be carrying Russian weaponry to Syria, apparently turned back towards Russia.
Russia's Interfax news agency reported on Monday that Russia was preparing to send marines to Syria in the event that it needs to protect personnel and remove equipment from the naval facility. It cited two large landing ships.
Syria is Moscow's firmest foothold in the Middle East, buys weapons from Russia worth billions of dollars and hosts the Russian navy's only permanent warm water port outside the former Soviet Union.
But Russia has faced increasing Western criticism over arms supplies to Syria, where the United Nations says government forces have killed more than 10,000 people in a crackdown.