Russia, the United States, European and Middle Eastern countries agreed last month on a two-year timeline leading to Syrian national elections, but left many questions unresolved, most notably the fate of Syrian president Bashar al-Assad.
The countries involved in the talks, which also include Saudi Arabia, Iran and Turkey, laid out a plan including formal talks between the government and opposition from January 1.
To achieve that timeline, Saudi Arabia is hosting a conference this week to try to unite Syria’s divided rebel and opposition groups, who are trying to forge a common platform to be able to negotiate with the Syrian government.
“Depending on the outcome of both the Saudi-led conference of the opposition that is taking place in the next days, as well as a few other issues, it is our plan to try … [to] have a meeting in New York on December 18,” Mr Kerry said.
“But again, it depends on the flow of events over the next week.”
A key issue for a ceasefire will be determining which groups fighting Mr Assad will be branded moderate opposition fighters deserving of a seat at the negotiating table and which will be labelled terrorists.
Opposition groups deemed legitimate will be invited to take part in the ceasefire while those labelled terrorists, so far Islamic State and al-Qaeda-linked groups, will be treated as fair game for Syrian government forces, Russia, the United States, France and others conducting air strikes in Syria.
“It is absolutely necessary that as was agreed in Vienna, there should be a nationwide ceasefire as soon as possible,” UN secretary-general Ban Ki-moon said.
“In New York I hope we will have a firm and solid basis so that the ceasefire can be launched as well as the political process.”