JUDY WOODRUFF: President Obama voiced new concerns about the Syrian war and the alleged use of chemical weapons to Russian President Putin today. They spoke in a phone call on a day when the Syrian prime minister narrowly missed being killed by a bomb in Damascus.
The bomb blast ripped through cars and buses in the Syrian capital, shattering windows and sending the wounded to the hospital.
MAN: I just heard a very loud sound. I didn't look around. I tried opening a door, but it wouldn't open. My uncle, a professor at the university, died beside me.
JUDY WOODRUFF: State TV said Prime Minister Wael al-Halqi, the intended target, was unhurt. He was later seen presiding over a meeting of economic advisers without any indication of when the footage was shot. And in recorded comments, Halqi mentioned today's date, but not the bombing. Instead, the state news agency quoted him as saying it shows the rebels are bankrupt.
There have been other high-profile attacks in Damascus in the last year. Today's came amid rising tensions on a different front, U.S. claims that the Syrian regime twice likely deployed chemical weapons in recent weeks.
SEN. LINDSEY GRAHAM, R-S.C.: It's going to become a failed state by end of the year. It's fracturing along sectarian ethnic lines. It's going to be al-Qaida's safe haven.
JUDY WOODRUFF: On Sunday, Republican Sen. Lindsey Graham of South Carolina said the U.S. must take action.
LINDSEY GRAHAM: There's nothing you can do in Syria without risk, but the greatest risk is a failed state with chemical weapons falling in the hands of radical Islamists and they are pouring into Syria.
JUDY WOODRUFF: Fellow Republican John McCain called for giving military aid to the Syrian rebels. And he said there might be a need for outside forces, but not involving Americans.
SEN. JOHN MCCAIN, R-Ariz.: We have to, as an international group, plan and be ready operationally -- not just plan, but be ready operationally, to go in and secure those areas. Whatever the composition of that force is, is something I think we have to look at very carefully. But the worst thing the American -- the United States could do right now is put boots on the ground in Syria. That would -- that would turn the people against us.
JUDY WOODRUFF: Today, White House spokesman Jay Carney turned aside talk of immediate action. He repeated that the administration wants to make sure it has all the facts.
JAY CARNEY, White House Spokesman: We have established with varying degrees of confidence that there have been incidents of chemical weapons used, sarin in particular, in a limited fashion in Syria. We're now working to build upon that evidence to increase the amount of evidence to find specifically what happened, what occurred, who was responsible, and build that case, if you will.
JUDY WOODRUFF: And Defense Secretary Chuck Hagel said that assessment is ongoing.
Meanwhile, the civil war in Syria continues, with more than 70,000 dead, and nearly 1.5 million Syrian refugees in surrounding countries.