Russia has sent sophisticated anti-ship missiles to Syria, according to a media report.
The New York Times quotes unnamed U.S. officials as saying the missiles could be used to counter any potential future foreign military intervention in Syria.
Without confirming details, Russia’s Foreign Minister Sergei Lavrov said Russian supplies did not break any international rules.
The report comes amid growing alarm that chemical weapons may be being used in Syria, something U.S. President Barack Obama has said would be “a red line”.
Meanwhile efforts continue to arrange an international conference on Syria.
The United Nations Secretary General Ban Ki-moon met Lavrov in the southern Russian city of Sochi on Friday to discuss plans for the conference, which would aim to bring together the Syrian opposition and members of President Bashar al-Assad’s government.
At a news briefing, Ban said it was important to “not lose momentum” on the drive towards holding a peace conference and dates for it were being “actively discussed.”
Lavrov said a resolution could only be found through “an inclusive, all Syrian dialogue with participation of all Syrian forces, without any external intervention, as soon as possible.”
Also on Friday, the U.N. refugee agency said more than 1.5 million Syrians were now registered as refugees, with the true figure likely to be much higher.
“Refugees tell us the increased fighting and changing of control of towns and villages, in particular in conflict areas, results in more and more civilians deciding to leave,” the agency said in a statement.
Russia is one of Syria’s few remaining allies and its major arms suppliers. Over the years, in contracts worth billions of dollars, it has sold thousands of tanks, artillery units, aircraft, helicopters and defense systems to Damascus.
According to the New York Times report, a recent Russian shipment to Syria included an advanced form of the Yakhont, a 22 foot-long missile with a range of 180 miles, and carrying either a high-explosive or armor-piercing warhead.
Read more: BBC