WASHINGTON — The attack that killed 26 people in northern Syria last week exposed the difficulty of determining whether the Syrian regime has resorted to chemical weapons as well as the lingering uncertainty over how President Obama would respond if what he has called a “red line” is crossed.
Current and former U.S. officials admitted that confirming a small-scale chemical weapons attack poses technical challenges because U.S. spy agencies cannot gather reliable intelligence, let alone air or soil samples, inside Syria.
U.S. intelligence analysts are still working to determine whether the attack near Aleppo on Tuesday involved the use of chemical compounds. The Syrian government and rebels have accused each other of unleashing the weapons.
The course Mr. Obama intends to take if confronted with proof is equally unclear.
The Pentagon has prepared calibrated options, ranging from airstrikes to sending troops to seize weapons sites.
But officials said they haven’t taken the advance steps needed to carry out such orders because planning has been hobbled by worries about the political backlash to a potential U.S. intervention as well as struggles to coordinate with regional allies.
“If we had to go in tomorrow, I’d say we aren’t ready,” said an Obama Administration official involved in preparations for securing Syria’s chemical weapons. “One thing we want to avoid is having one group securing the sites and another group bombing them.”
The level of uncertainty surrounding U.S. contingency planning two years into a conflict that has killed more than 70,000 people contrasts with the clarity of Mr. Obama’s repeated admonitions to President Bashar Assad’s government.
After initial reports indicated chemical weapons may have been used in the attack near Aleppo last week, Mr. Obama said such a step by Assad would be a “game changer.”
He said he had instructed his “teams” to “find out precisely whether or not this red line was crossed.”
The United States has worked with regional allies to prepare responses if the regime uses its chemical weapons or if events require seizing weapons sites.
Some of the largest depots are near Syria’s border with Jordan. The administration has sent thousands of protective suits and more than 150 military personnel to help train Jordanian special-forces teams to secure weapons sites, according to U.S. and Middle Eastern officials.
The ambiguous U.S. response has exposed Mr. Obama to growing criticism.
Rep. Mike Rogers (R., Mich.), the chairman of the House Intelligence Committee, mocked Mr. Obama in a series of appearances last week. In a PBS interview, Mr. Rogers said that the U.S. threshold for action “can’t be a pink line. It can’t be a dotted line. It can’t be an imaginary line.”
U.S. intelligence officials and weapons experts said emerging information indicates that chemical weapons were not used. The administration officials said victims appeared “asymptomatic” for chemical-weapons exposure. Outside experts also have voiced skepticism, noting that footage showed that medical personnel treating victims did not don protective garments or masks.
If there had been an attack with sarin or VX gas, the deadliest agents in Syria’s extensive arsenal, most of the people present would have been fatally or seriously contaminated, said Jean Pascal Zanders, a chemical weapons expert for the European Union.
“Fatalities happen literally within minutes or even seconds,” he said. “There’s nothing that suggests that these people were even remotely exposed to nerve agents.”
U.S. officials said it is likely the physical evidence will be scant by the time experts reach the village where the attack occurred, so experts must rely mainly on witness reports and monitoring the symptoms of those who may have been exposed. The officials also said that the CIA does not have a presence in Syria and the scope of the conflict has precluded it from distributing sensors that could detect chemical attacks.
Meanwhile, the Western-backed opposition plunged into disarray as its president quit and its military leader refused to recognize a prime minister recently elected to lead an interim rebel government. The chaos inside the Syrian National Coalition threatened to undermine its bid to unite the forces battling Assad and better organize the fight to oust his regime.
In his surprise resignation Sunday, coalition president Mouaz al-Khatib expressed frustration with the international community and the opposition body itself.
Secretary of State John Kerry said he was sorry to learn of Mr. al-Khatib’s resignation but said that it won’t affect U.S. cooperation with the coalition on aid. Mr. Kerry called such transitions natural, adding that it shows “an opposition that is bigger than one person, and that opposition will continue.”
The second blow Sunday to the opposition leadership was delivered by the head of the coalition’s own military branch, Gen. Salim Idris, who refused to recognize the body’s new prime minister, saying he did not represent many anti-Assad groups.
Last week, the coalition elected a U.S.-educated IT expert named Ghassan Hitto to head a rebel interim government. But in a video statement posted online and distributed by his aides Sunday, General Idris said his group would only support a prime minister with broad backing.