Good morning and welcome to "this week." Stunner, the commander in chief decides to strike syria. We cannot turn away from the massacre of civilians, chemical weapons. I'm asking congress to send a... See More
Good morning and welcome to "this week." Stunner, the commander in chief decides to strike syria. We cannot turn away from the massacre of civilians, chemical weapons. I'm asking congress to send a message to the world. Will they approve, what if they don't, what are the risks of delay? We're live with terry moran in the middle east, christiane amanpour from london. These are the facts. I'll go one-on-one with the man who made america's case to the world. Secretary of state john kerry. Plus the team of experts is here to break down the global and military consequences of the president's decision. And we weigh in on the politics of war and the fallout at home. It's all right here this sunday morning. Hello, again, when president obama took to the rose garden saturday afternoon, his first words had been telegraphed for days. I have decided that the united states should take military action against syrian regime targets. Then the twist. The president's top military adviser joint chiefs chair martin dempsey said there was no need to attack now. The chairman indicated to me our capacity to execute the mission is not time sensitive. It will be effective tomorrow or next week or one month from now. And I'm prepared to give that order. But only after congress votes. I will seek authorization for the use of force from the american people's representatives in congress. For the last several days, we have heard from members of congress who want their voices to be heard. I absolutely agree. It is a high-stakes bet. We're going examine the squoepss with secretary of state john kerry and our team of experts and correspondents in the studio and around the world. We start at the white house with jon karl. This didn't just surprise us, the president kept the team in the dark until late friday. Reporter: It sure did, george. This was a total reversal for the president. Until late friday, this was an idea that wasn't under consideration. None of the senior advisers were pushing for congressional authorization. It was not the direction they were pushing, but he decided after the vote in britain, this was the direction he had to go. Take a look at the photo in the situation room before the president announced the decision on saturday. As you can see, grim faces all around. There were serious concerns expressed by his national security team. Concerns chief among them that congress could vote no on his request for authorization. That's the big question. He would be the first president in modern times to lose a vote for military force. Where are the votes now? Reporter: I talked to a senior republican just a short while ago, if the vote were held right now in the house, he believes that the president would lose. There's a lot of work to be done. That republican thinks ultimately the president can get authorization, but he is going to need to get a lot of democratic votes, including a lot of democrats generally reluctant to authorize the use of force. This could be a nail biter, especially in the house. Thanks. Let's get to the military implications with martha raddatz. One person the president didn't consult early was general dempsey. He gave him the cover he needed. He gave him cover and it's real. Martin dempsey said it was just as effective today, tomorrow, or a month from now. And think of it this way, it's like a feint. The enemy, we watch the enemy, we watch the syrian regime and how they responded to the idea of an attack. Where they started moving things. It may be more effective a month from now, because we can train more, we can watch what the syrian regime does and respond. They were ready. They had those destroyers in the mediterranean ready to go. This is still a limited strike. They say a limited strike to prevent and deter any more chemical attacks. For syria, we go to terry moran in beirut. And apparently, a lot of relief in damascus. Reporter: A lot. This was more than good news, they claimed a victory in damascus. Both the assad regime and his supporters. There are many of them here. The deputy prime minister saying it was the syrian army that warded off the aggression of the united states. And in fact they believed that the unified front that they had with iran and with hezbollah has essentially frightened president obama into backing down from his attack. Now, they also know that the congress could authorize the use of force, but this delay gives them even more time to prepare. Church bells rang out, there were prayers sounding around damascus. This came as a shock and a good one to the people of damascus. Not a good shock for the rebel leaders in syria. Reporter: Devastating, george. On twitter and in public statements, leaders of that fractured opposition in syria are expressing disappointment and disillusion with american leadership. One of the leaders of one of those factions said the people of syria are all alone now. They believe that the chemical weapons attack they argue was carried out by the regime was with impunity, and the world is not ready to do anything. Obama's leadership image in the syrian opposition is probably at an all-time low right now, george.
This transcript has been automatically generated and may not be 100% accurate.