The White House could release evidence the Syrian government used chemical weapons on its own people as early as Thursday, CNN's Barbara Starr reports.
In an interview with PBS Newshour, the President left no doubt who the U.S. believes ordered the chemical weapons attacks, saying:
"We want the Assad regime to understand that by using chemical weapons on a large scale against your own people – against women, against infants, against children, that you are not only breaking international norms and standards of decency, but you're also creating a situation where U.S. national interests are affected, and that needs to stop."
Among the evidence proving the Syrian regime's hand behind chemical weapons use: intercepts of Syrian commanders discussing the movement of chemical weapons to the area of the attack, provided by Israeli intelligence.
The U.S.'s potential next step, launching cruise missile strikes, has put the U.S. at direct odds with Russia.
"We do not believe the Syrian regime should be able to hide behind the fact that the Russians continue to block action on Syria at the U.N., State Department Deputy Spokesperson Marie Harf tells the press.
"But behind the scenes officials are signalling the U.S. may not wait for the U.N. to act," Starr says.
"The U.S. military is strengthening its position in the Eastern Mediterrrean with the addition of two more submarines."
The Syrian regime is also getting prepared.
Bashar al-Jaafari, Syria's ambassador to the UN, says "We are in a state of war right now preparing ourselves for the worst scenario."
But the rhetoric from the Syrian government has also become more subdued now.
"You can tell that the regime is getting more and more nervous," reports CNN's Frederik Pleitgen.
Pleitgen says many Syrians are also getting fearful and trying to leave the country now.
“People seem unsure what the future will bring with the American air strikes looming.”