A senior administration official said Sunday there is "very little doubt" that a chemical weapon was used by the Syrian regime against civilians in an incident that killed at least 100 people last week, but added that President Barack Obama had not yet decided how to respond.
The official said the US intelligence community based its assessment given to the White House on "the reported number of victims, reported symptoms of those who were killed or injured," and witness accounts. The official spoke on condition of anonymity because the official was not authorized to speak publicly.
The official said the White House believes the Syrian government is continuing to bar a U.N. investigative team immediate access to the site of a reported Aug. 21 chemical weapons attack in the Damascus suburbs, in order to give the evidence of the attack time to degrade.
The US official said the regime's continuing shelling of the site also further corrupts any available evidence of the attack.
Syrian state media, however, reported Sunday that Syria's government has reached an agreement with the United Nations to allow a U.N. team of experts to visit the site of last week's alleged chemical weapons attack.
Last Wednesday's purported chemical attack in the Damascus suburb of eastern Ghouta has prompted US naval forces to move closer to Syria. Obama met with his national security team Saturday to assess the intelligence and consider a US military response, almost a year after warning the regime of Syrian President Bashar Asad that chemical weapons use was a "red line" for the United States.
The White House had concluded previously that the Syrian regime has used chemical weapons in limited incidents, but last week's attack is suspected of being the deadliest single incident of a civil war that has killed more than 100,000 people since March 2011.
US Defense Secretary Chuck Hagel said on Thursday that a chemical attack "appears to be what happened."
The White House has approved limited lethal aid to Syrian rebels, but has limited weapons to mostly small arms and training. Obama described the factors limiting greater US involvement in a CNN interview.
"If the US goes in and attacks another country without a U.N. mandate and without clear evidence that can be presented, then there are questions in terms of whether international law supports it — do we have the coalition to make it work?" Obama said in the interview broadcast Friday. "Those are considerations that we have to take into account."
Hagel offered no hints Sunday about likely US response to Syria's purported use of chemical weapons, telling reporters traveling with him in Malaysia that the Obama administration was still assessing intelligence information about the deadly attack.
"When we have more information, that answer will become clear," he said when a reporter asked whether it was a matter of when, not if, the US will take military action against Syria.
Asked about US military options on Syria, Hagel spoke in broad terms about the factors Obama is weighing.
"There are risks and consequences for any option that would be used or not used — for action or inaction," he told reporters. "You have to come to the central point of what would be the objective if you are to pursue an action or not pursue an action. So all those assessments are being made."
If the US wants to send a message to Assad, defense officials have previously indicated the most likely military action would be a Tomahawk missile strike, launched from a ship in the Mediterranean.
Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said in a letter to a US congressman last week that the administration opposes even limited action in Syriabecause it believes rebels fighting the Assad government wouldn't support American interests if they seized power. He said the US military could take out Assad's air force and shift the balance of the war toward the armed opposition, but it's unclear where the strategy would go from there.
Dempsey is now in Amman, Jordan, set to meet with Arab and Western peers later Sunday to discuss ways to bolster the security of Syria's neighbors against possible attacks, chemical or other, by Assad's regime, a Jordanian security official said.
The meeting, closed to the press and held at an unspecified location, gathers chiefs of staff from Britain, France, Germany, Italy, Canada, Turkey, Saudi Arabia, Qatar and Jordan, the official said on condition of anonymity because he is not allowed to brief reporters.
Associated Press National Security Writer Robert Burns contributed to this report from Kuala Lumpur, Malaysia, and AP writer Jamal Halaby contributed from Amman, Jordan.