U.S. President Barack Obama has ordered local spy agencies to urgently probe claims that Syrian forces launched a horrific chemical attack on civilians, including children, aides said Thursday.
Officials said they could not yet be sure the deadly arms had killed as many as 1,300 people outside Damascus, as the rebels have claimed.
The Obama administration is facing rising political pressure for a tough response to the attack, which could have again infringed U.S. "red lines" against chemical weapons use by President Bashar Al-Assad's regime.
State Department spokesman Jen Psaki said that Obama had asked intelligence agencies to urgently evaluate claims by Syrian rebels about the attack.
"Right now, we are unable to conclusively determine CW (chemical weapons) use," Psaki said, according to the AFP news agency.
She added, however, that the administration had been focused continually since reports of the attack broke on Wednesday on efforts to "nail down the facts."
Secretary of State John Kerry discussed the incident with key counterparts, including Syria's main opposition leader Ahmad Assi Jarba and French Foreign Minister Laurent Fabius.
Kerry also called top officials at the European Union, the United Nations and in Jordan, Qatar and Turkey.
"If these reports are true, it would be an outrageous and flagrant escalation of (the) use of chemical weapons by the regime," Psaki said.
Obama has a range of options at his disposal and would discuss a response with his top national security aides, Psaki said, according to AFP.
Republican Senator John McCain warned that Obama had given Assad a "green light" to commit atrocities by failing to use military force to respond to previous chemical attacks.
"When the president of the United States says that if he uses these weapons that it would be a, quote, 'red line and a game-changer,' (Assad) now sees that as a green light," he told CNN.
"The word of the president of the United States can no longer be taken seriously, as it isn't throughout the entire region," said McCain.
The White House concluded earlier this year that Syria had crossed Obama's red line against the use of chemical weapons, but opted not to take military action.
Instead, it decided to directly arm selected Syrian rebel groups battling Assad -- but has declined to publicly specify the extent of the support.
France's foreign minister, Laurent Fabius, said in a television interview Thursday that the use of chemical weapons by Bashar al-Assad, if proven, should lead to the use of force by other countries against Syria – but he ruled out a ground invasion.
“If it is proven, France's position is that there must be a reaction, a reaction that could take the form of a reaction with force,” Fabius told BFM-TV.
“There are possibilities for responding,” he said without elaborating.
He said, however, that there was “no question” of sending in ground troops, adding “it's impossible.”
The United Nations Security Council held an emergency meeting on Wednesday on the alleged attack, and at the end concluded that it was necessary to “clarify” the.
The Council stopped short of demanding a probe by UN investigators currently in Syria, due to opposition by Russia and China, key allies of Assad that have already vetoed several Security Council resolutions condemning his regime.
The Chairman of the Bayit Yehudi party, Minister Naftali Bennett, called for an end to the world’s silence over the chemical weapons attack in Syria.
“Seventy years ago,” he wrote on his Facebook page, “when children and babies were murdered, the world stayed silent.”
“Today, too, the world is silent to the terrible massacre in Syria. Television and Internet aren't waking up the world.
“Piles of dead children cannot be ignored. We will NOT be silent.
“The Jewish People, and I, as a minister in the government of the Jewish state, have a special duty to speak up, to yell, so the world will hear and stop ignoring what's going on in Syria.
“That's our moral duty. Please ACT and SHARE this NOW.”