The United States has made it clear that it would punish the Syrian President, Bashar al-Assad, for the “brutal and flagrant” chemical weapons attack that it said killed 1,429 people near Damascus last week.
The US Secretary of State, John Kerry, said on Friday that the dead included 426 children.
In a speech at the State Department, he described the attack as an “inconceivable horror”.
President Barack Obama later said the US was considering a “limited narrow act” in response to the attack, which posed “a challenge to the world”.
“We are not considering any kind of military action that involves boots on the ground or a long-term campaign,” he said.
But Obama said the use of chemical weapons threatens US national security and merits a response.
The Syrian Foreign Ministry has dismissed Kerry’s statement as “full of lies” based on “fabricated evidence”, insisting the rebels carried out the deadly attack.
State-run news agency SANA said Kerry, who cited a US intelligence report, was using “material based on old stories that the terrorists have been circulating for more than a week”.
The intelligence gathered for the US report included an intercepted communication by a senior official intimately familiar with the August 21 attack as well as other intelligence from people’s accounts and intercepted messages, the four-page report said.
Kerry said their report would only confirm that chemical weapons were used, and he made clear that would not change much for Washington since “guaranteed Russian obstructionism” would make it impossible for the UN to galvanise world action.
“The primary question is really no longer, what do we know. The question is, what are we – we collectively – what are we in the world going to do about it,” Kerry said.
He said the president had been clear that any action would be “limited and tailored” to punishing Assad, that it would not be intended to affect the civil war there and Washington remained committed to a diplomatic solution to the crisis, after Assad seemed to have intentionally defied the US by crossing the red line on chemical weapons use drawn by President Obama months ago.