The agreement will create a roadmap toward a peace process end the five-year civil war in Syria, and was drafted earlier on Friday.
Participants in the Friday talks preceding the adoption of the resolution included UN Secretary General Ban Ki-moon, UN envoy to Syria Staffan de Mistura, Russian Foreign Minister Sergei Lavrov, US Secretary of State John Kerry, as well as Arab League and Organization of Islamic Cooperation representatives.
"The result of the voting is clear, the draft resolution has received 15 votes in favor. Therefore the draft resolution has been adopted unanimously," US Secretary of State John Kerry said during the meeting.
"The resolution we just reached is a milestone, because it sets specific goals and specific timeframes," he said, adding that "there obviously remain sharp differences within the international community, especially about the future of President Assad."
The resolution includes preparations for a ceasefire monitoring mechanism that would come into effect "as soon as the representatives of the Syrian government and the opposition have begun initial steps towards a political transition under UN auspices," according to Reuters.
Talks with the Syrian opposition are set to begin in early January, and the draft "demands that all parties immediately cease any attacks against civilians and civilian objects," and "stresses that the Syrian people will decide the future of Syria."
The resolution sets a target of six months for the government transition, while elections are planned to be held within 18 months.
It "reconfirms its endorsement of the Geneva Communiqué of 30 June 2012, endorses the 'Vienna Statements' in pursuit of the full implementation of the Geneva Communiqué, as the basis for a Syrian-led and Syrian-owned political transition in order to end the conflict in Syria, and stresses that the Syrian people will decide the future of Syria."
The document also expresses support "for a Syrian-led political process that is facilitated by the United Nations and, within a target of six months, establishes credible, inclusive and non-sectarian governance and sets a schedule and process for drafting a new constitution, and further expresses its support for free and fair elections, pursuant to the new constitution, to be held within 18 months and administered under supervision of the United Nations."
Only the Islamic State, or Daesh, and the al-Nusra terrorist groups will be exempt from a ceasefire that the UN Security Council is hoping to broker through the Vienna process.
"It is our hope that a nationwide ceasefire can go into effect excluding only Daesh and al- Nusra and any other group that we might decide at some time to designate," Kerry stated on Friday after the passage of the resolution.
