Transcript for Trump says Syria chemical attack 'crossed many, many lines'

President trump taking on the crisis in Syria saying the chemical attack crossed many lines. Here is what we know this morning. Reports say at least 80 people were killed. Making this the deadliest chemical attack there since 2013. The Syrian civil war is now in its seventh year. Russia has an estimated 4,000 troops in Syria. America has about 900 troops training and assisting rebel forces to fight ISIS. Let's go straight now to our chief foreign correspondent Terry Moran from London with more. Good morning. Reporter: Good morning, Amy. There's mounting evidence this morning and strong denials. A total denial was issued that the Syrian government perpetrated the chemical attack. Instead he blamed rebels for stockpiling chemical weapons that he claims were released by a government air strike, but experts and doctors treating the victims say that's just not possible. President trump says Tuesday's deadly chemical attack in Syria has gone too far. That crosses many, many lines beyond a red line. Reporter: Standing alongside a key U.S. Ally in the middleeast king Abdullah of Jordan he declared he has a new stance on the Syrian civil war. It's already happened that my attitude toward Syria and Assad has changed very much. Reporter: He's still placing the blame squarely on the Obama administration. The Obama administration had a great opportunity to solve this crisis a long time ago when he said the red line in the sand. It is now my responsibility. Reporter: The rocket explosions are now believed to have exposed hundreds of Syrian civilians to a combination of chlorine gas and sarin. How the U.S. Responds now is a critical test of the white house's relations with Russia, Syria's key backer. We cannot close our eyes to those picture. We cannot close our minds of the responsibility to act. Reporter: And high drama at the U.N. Security council where U.S. Ambassador Nikki Haley leveled harsh charges right at Russia. Russia cannot escape responsibility for this. Reporter: But when he was asked whether he planned to take military action, draws his own red line the president declined to say. Terrible affront to humanity. I can tell you, terrible. Will you take action against Syria? You'll see. Reporter: The real problem for president trump as it was for Obama what can be done? Punitive air strikes are one option but even limited steps like that can have unexpected consequences including potential Russian casualties given how many Russian boots are on the ground throughout Syria right now. It's a real problem, George.

This transcript has been automatically generated and may not be 100% accurate.