UN Security Council members unanimously approved a UN resolution Friday endorsing a peace process for Syria including a cease-fire and talks between the Damascus government and the opposition, but the draft makes no mention of the most contentious issue -- the future role of Syrian President Bashar Assad.

The resolution makes clear that the blueprint it endorses will not end the conflict, deep into its fifth year with well over 300,000 killed, because "terrorist groups," including the Islamic State group and the al-Qaida-linked al-Nusra Front, are not part of the cease-fire.

U.S. Secretary of State John Kerry praised "the unprecedented degree of unity" in the council, which has been stymied in the past over a political solution in Syria, and called the resolution "a milestone."

Foreign ministers from 17 countries met for more than five hours on how to implement their call in Vienna last month for a cease-fire and the start of negotiations between the government and opposition in early January. At the same time, diplomats worked to overcome divisions on the text of the resolution.

The resulting agreement "gives the Syrian people a real choice, not between Assad and Daesh, but between war and peace," Kerry said, using the Arabic acronym for the Islamic State extremists.

"We're under no illusions about the obstacles that exist ... especially about the future of President Assad" where "sharp differences" remain, Kerry said.

But he made clear that Assad must go if there is to be peace in Syria.

"Assad has lost the ability ... to unite the country," Kerry said. "If the war is to end, it is imperative that the Syrian people have to agree on an alternative" to their government.

Secretary-General Ban Ki-moon said Syria was "in ruins," singling out besieged areas where "thousands of people have been forced to live on grass and weeds," which he called "outrageous."

"This marks a very important step on which we must build," Ban said of Friday's resolution.

At an earlier ministerial meeting, Ban said he urged the government and opposition to implement confidence-building measures, including a halt to the use of barrel bombs and other indiscriminate weapons against civilians, as well as granting unconditional access to aid convoys, lifting restrictions on the delivery of medical aid and releasing all detainees.

Ministers said they would meet again in January.

The resolution calls on the secretary-general to convene representatives of the Syrian government and opposition "to engage in formal negotiations on a political transition process on an urgent basis, with a target of early January 2016 for the initiation of talks."

Within six months, the process should establish "credible, inclusive and non-sectarian governance," and set a schedule for drafting a new constitution. UN-supervised "free and fair elections" are to be held within 18 months under the new constitution.

The resolution calls the transition Syrian-led and Syrian-owned, stressing that the "Syrian people will decide the future of Syria."

The resolution also says cease-fire efforts should move forward in parallel with the talks, and it asks Ban to report within a month on ways to monitor the cease-fire.

Still, it notes that the cease-fire "will not apply to offensive or defensive actions" against the Islamic State group and al-Nusra Front. This means that airstrikes by Russia, France and the U.S.-led coalition apparently would not be affected, nor would military action by the extremists.

Jordanian Foreign Minister Nasser Judeh said he presented lists submitted from each country of groups they consider terrorist organizations. He said some countries "sent 10, 15, 20 names" and others more.

"Now I think there will be follow-up steps in terms of countries meeting again to set criteria which will help filter the list," Judeh said.

Russian Foreign Minister Sergey Lavrov stressed that "terrorists of all stripes have no place in the talks."

"It is inadmissible to divide terrorists among good and bad ones," he said.

Those around the table included the United States, key European nations and Saudi Arabia, who support the Syrian opposition, and the Assad government's top allies, Russia and Iran.

Chinese Foreign Minister Wang Yi said the two most important issues are launching political negotiations among Syrian parties and implementing a UN-monitored cease-fire. "Without peace talks, the cease-fire cannot be sustained. Without a cease-fire, peace talks cannot continue to produce results," he said.

Wang noted the "severe threat posed by international terrorism," a reference to the Islamic State group, which has exploited the chaos to seize large parts of Syria.

The peace plan agreed to in Vienna last month by 17 nations as well as the UN, European Union, Arab League and Organization of Islamic Cooperation sets a Jan. 1 deadline for the start of negotiations between Assad's government and opposition groups.

That deadline is "too ambitious a timetable," the UN representative for the Syrian National Coalition, the main Western-backed opposition group, told reporters Friday. Najib Ghadbian estimated that a month of preparation is needed.

Ghadbian also said a comprehensive solution to the conflict requires "the removal of all foreign troops from Syria, all of them," including Russia, which began a campaign of airstrikes in September that have focused on more moderate forces fighting Assad in areas where the Islamic State group has little or no presence.

The co-ordinator of the opposition team that will negotiate with the Syrian government, former Prime Minister Riad Hijab, said in Saudi Arabia on Friday that Assad should have no role during a transitional period. He also called for "confidence-building measures" such as the lifting of a siege imposed on rebel-held areas and a halt to airstrikes.

Associated Press writer Bassem Mroue in Beirut contributed.