JUDY WOODRUFF: As we just reported, late this afternoon, the 15 nations on the United Nations Security Council voted unanimously to endorse a framework for a peace process in Syria, after nearly five years of brutal civil war that's left more than 250,000 dead and millions displaced.

For more, we go to Hari Sreenivasan.

HARI SREENIVASAN: And with me to explore the details of this deal, what's at stake, and the long road to this point is chief foreign affairs correspondent Margaret Warner.

So, we've seen the headline during the day. How significant is this?

MARGARET WARNER: This is a very deal, Hari. You've got all the members of the Security Council, not just the members to have the region who have been involved in this, but all the members of the Security Council, some of who vehemently disagreed about the future of Syrian President Bashar al-Assad, to agree on resolutions setting up the process that will set up not only a cease-fire between Assad and many of his opposition groups on the ground but direct talks between the two of them. And it now has the imprimatur of the U.N. Security Council, and Ban Ki-moon, the secretary-general, committed to help implement it.

HARI SREENIVASAN: So, there'd been a lot of countries working toward this, but there are four major players and smack-dab in the middle of all this is Bashar al-Assad.

MARGARET WARNER: That's right. The major division among many concerns his future. On one side, you've got the United States and the Gulf states who began all this wanting Assad gone as soon as possible, and both have supported opposition groups on the ground in different ways. But on the other side you've got Russia and Iran, both of them regard Syria, and Syria is a client state for different reasons. Both of them have sent military assistance weapons advisors, even fighters, and in Russia's case bombs, to try to shore him up.

HARI SREENIVASAN: And there's tensions between the United States and Russia.

MARGARET WARNER: Yes, that's very true. Then you have another cross-cutting tension between the U.S. and Russia, which would be for influence in this process. For a long time, Russia wasn't very involved and then it inserted itself in September by beginning this bombing, and won itself a place at the table, because they want influence over the outcome.

HARI SREENIVASAN: And Saudi Arabia and Iran have their tensions.

MARGARET WARNER: They certainly do. And, in fact, that's part of the knob of all of this. Saudi Arabia, leader of the Sunni states in this region, and Iran, of course, Shiite state, huge historical rivalry for primacy in this region.

HARI SREENIVASAN: All right. So, what did peace players all actually get over their disagreements and agree to?

MARGARET WARNER: Which really is incredible. I think it's two things, Hari. One is threat of international terrorism. Even the Chinese foreign minister this to reporters today, we've got to get the process going because of threat of international terrorism.

They have come to the conclusion that they can never take on ISIS until the boil of the Syrian conflict, until they launch that boil. That remember was the original, not only attracter but incubator of all of the thousands of foreign fighters coming in, helping beef up this al-Qaida in Iraq that became ISIS, helping them establish them this caliphate in the ungoverned portion of eastern Syria and roll on into Iraq and they recognize there's no way to take them on.

The second thing that they've agreed on is that, militarily, it can't be solved. Every one of them, these four countries, has supported different groups on the ground and they now all realize they have been sucked into a quagmire. There is no military resolution, has to be political.

HARI SREENIVASAN: All right. So, one thing at the dead center of all this is Assad. The next steps here, this agreement doesn't mention him by name, which is one of those central tensions you mentioned.

MARGARET WARNER: Absolutely, and they had to do it that way because the differences remain and so they had to finesse it. They talk about a political transition. The United States believes if you have a transition to an inclusive nonsectarian government which is its language they've agreed on, there is no way an autocrat for minority Alawites can be head of that government, so they think you'll eventually get to that point and the Russians have signaled the United States they're not so much wedded to Assad as the idea of a unitary state.

So the steps are a very, very tall order, which is to set up both the cease-fire in January and these direct talks. I think it's going to be very hard. There are other disagreements, including who gets to sit in for the opposition. This is just one step in other words of trying to maintain the momentum to get to the political resolution.

HARI SREENIVASAN: And getting to the cease-fire, you have to know who's on which side of the table.

MARGARET WARNER: Right.

HARI SREENIVASAN: I mean, who exactly is the enemy of Assad, which countries think should be at the table.

MARGARET WARNER: Very important point.

The opposition, which have never agreed on anything, finally had a meeting in Riyadh a week ago and they actually chose the group that then will choose the group to sit at the table, OK? It's very indirect.

But meanwhile, all these other countries, all of them, have different candidates that they want to nominate for too much of the terrorist to be at the table. So, they include some groups that have been clients of Iran, some of them clients of Saudi Arabia. All of that is still unresolved. Jordan is supposed to be coordinating this, poor Jordan, so that all remains to be resolved.

HARI SREENIVASAN: So, big first step today.

But thank you very much, Margaret Warner.

MARGARET WARNER: My pleasure.