WASHINGTON — U.S. and allied intelligence agencies have made a preliminary assessment that chemical weapons were used by Syrian forces in an attack near Damascus this week, likely with high-level approval from the government of Syrian leader Bashar Assad, according to American and European security sources.
President Obama, in his first public comments since Wednesday’s attack that killed at least 100 civilians and possibly many more, said the United States is still trying to find out what happened.
He called the incident a “big event, of grave concern” that demands U.S. attention, but he said he is in no rush to get war-weary Americans “mired” in another Middle East conflict.
The President made his remarks as senior U.S. officials weighed choices ranging from increased international sanctions to the use of force, including possible airstrikes on Assad’s forces, administration sources said.
Among the military options under consideration are targeted missile strikes on Syrian units believed responsible for chemical attacks or on Assad’s air force and ballistic missile sites, U.S. officials said.
Such strikes could be launched from U.S. ships or combat aircraft capable of firing missiles from outside Syrian airspace, thereby avoiding Syrian air defenses.
Seen as more risky — and unlikely — would be a sustained air assault, such as the one conducted in Libya in 2011.
The U.S. Navy has expanded its presence in the Mediterranean by positioning a fourth cruise-missile-armed warship in the region because of the civil war in Syria, a defense official said on Friday.
The official emphasized that the Navy had received no orders to prepare for any military operations regarding Syria.
The White House on Friday reiterated Mr. Obama’s position that he did not intend to put “boots on the ground” in Syria.
An administration official said a meeting of military and security officials at the White House late Thursday also steered clear of the idea of enforcing a “no-fly” zone there.
It appeared unlikely that any military response would take place without consultation with allies and further review of U.S. intelligence about the attack.
The Syrian government denies being responsible and has in the past accused rebels of using chemical weapons, an allegation that Western officials have dismissed.
While the preliminary U.S. assessment was that Assad loyalists carried out Wednesday’s attack with high-level authorization, one U.S. source monitoring events in the region said it also was possible that a local commander decided on his own to use gas to clear the way for a ground assault.
“What we’ve seen indicates that this is clearly a big event, of grave concern,” Mr. Obama said in an interview on CNN’s New Day program that aired on Friday, as anti-Assad rebels braved the front lines around Damascus to smuggle tissue samples to U.N. inspectors from victims of Wednesday’s apparent mass poisoning.
Asked about his comment — made a year and a day before the toxic fumes hit sleeping residents of rebel-held Damascus suburbs — that chemical weapons would be a “red line” for the United States, Mr. Obama expressed caution.
“If the U.S. 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,” Mr. Obama said. “The notion that the U.S. can somehow solve what is a sectarian complex problem inside of Syria sometimes is overstated.”
In Moscow, Russian officials urged Syria to allow U.N. investigators to examine evidence of the suspected chemical weapons attack, joining the United States in seeking a full accounting of what happened in the eastern suburbs of Damascus.
“The Russian side called on the Syrian government to cooperate with the U.N. chemical experts,” the Russian Foreign Ministry said.
The Russians have accused Syrian rebels of staging the attack to implicate Assad’s government.
The United States, France, and other countries have been pushing for an investigation into allegations that poison gas was used in the attack.
U.N. inspectors are already in Damascus, just a short drive away from the attack site, after arriving Sunday to investigate previous claims about chemical weapons.
Heavy fighting in the eastern suburbs has made it impossible for them to examine the new allegations, even as the passage of time renders the forensic evidence less valuable.
The British foreign secretary, William Hague, said Friday that the Syrian government was almost surely behind the suspected chemical weapons attack.
“I know that some people in the world would like to say that this is some kind of conspiracy brought about by the opposition in Syria,” he said. “I think the chances of that are vanishingly small and so we do believe that this is a chemical attack by the Assad regime.”
Mr. Hague also said that time was of the essence in getting U.N. weapons inspectors to the site.
“It seems the Assad regime has something to hide,” he said.
Mr. Hague did not speak of using force, as the French have done, if the government was found to have been behind the attack.
But he said it was “not something that a humane or civilized world can ignore.”