(Adds quotes, background on chemical weapons)
CAMP DAVID, Md., May 14 (Reuters) - President Barack Obama said on Thursday if reports of chlorine gas attacks in Syria were confirmed, the United States would work with the international community to put a stop to them.
At a news conference after his Camp David summit with Gulf allies, Obama said he has seen reports about the use of chlorine in bombs that have the effect of chemical weapons.
"And so we're working with the international community to investigate that," he said at the presidential retreat in Maryland.
While chlorine itself is not listed as a chemical weapon, its use in such attacks may be prohibited, Obama said.
The Organization for the Prohibition of Chemical Weapons has been investigating allegations of dozens of recent chlorine gas attacks in Syrian villages, but it is being refused access to the sites by President Bashar al-Assad's government, diplomatic sources said.
"If we have the kinds of confirmation that we need, we will once again work with the international community and the organization charged with monitoring compliance by the Syrian government, and we will reach out to patrons of Assad like Russia to put a stop to it," Obama said.
In 2013, the United States threatened military intervention against Syria's government after sarin gas attacks killed hundreds of people in a Damascus suburb.
"The reason we did not was because Assad gave up his chemical weapons," Obama said. "And that's not speculation on our part. That, in fact, has been confirmed by the organization internationally that is charged with eliminating chemical weapons."
Assad's government last year handed over 1,300 tons of chemical arms to a joint U.N.-OPCW mission for destruction. But Damascus has denied using sarin or any chemical weapons in battle during Syria's continuing civil war.
Some Western governments suspect that Assad withheld some of his stockpile. Reuters reported last week that international inspectors have found traces of sarin and VX nerve agent at a military research site in Syria.
Obama has been criticized as not being aggressive enough in confronting global crises including Syria, but he counts as his accomplishments an international deal to secure and eliminate Syria's chemical weapons stockpiles.
"I don't think that there are a lot of folks in the region who are disappointed that Assad is no longer in possession of one of the biggest stockpiles of chemical weapons of any country on earth," he said Thursday. "Those have been eliminated." (Reporting by Roberta Rampton and Doina Chiacu; Editing by Emily Stephenson and Eric Beech)