The United States is concerned about reports that Russia is moving more military materiel into Syria, Ben Rhodes, deputy national security adviser to President Barack Obama, said on Thursday.
"We've been concerned about reports of Russia moving materiel into Syria," he said at a press briefing in Saudi Arabia's capital Riyadh, where Obama was attending a summit with Gulf Arab leaders to discuss regional security issues.
"We think it would be negative for Russia to move additional military equipment or personnel into Syria," Rhodes said. "We believe that our efforts are best focused on supporting the diplomatic process."
Press reports in the United States have indicated that Russia has moved more artillery into Syria, weeks after declaring a partial withdrawal of its military presence there.
In late February, Syria's warring parties agreed to a cessation of hostilities, aimed to stop hostilities in the war torn country.
However, the “cessation of hostilities” did not include groups defined as “terrorist” by the UN Security Council.
But the agreement has been strained by renewed fighting and peace talks in Geneva also appear to have collapsed this week, with the opposition saying it has called for a "pause" in the negotiations.
Syrian opposition groups often express their concerns that Russia would use the terms agreed on by the sides and make it an ‘excuse’ to target opposition held areas, claiming to target ‘terrorist’ factions.