A meeting of UN, US and Russian envoys on Monday is expected to agree that a Syria peace conference should be held in January, diplomats said.
UN leader Ban Ki-moon is to announce the date shortly after the meeting in Geneva, the envoys said.
The conference on the worsening 32-month-old war has been repeatedly delayed amid wrangling over who should represent the Syrian opposition and government and whether countries such as Iran and Saudi Arabia should take part.
UN-Arab League mediator Lakhdar Brahimi, Russian deputy foreign ministers Mikhail Bogdanov and Gennady Gatilov and US Under Secretary for Political Affairs Wendy Sherman are to hold the Geneva talks on Monday.
"They have patched over enough of the differences that the conference will be held, but it will miss Ban's aim of December. It is now set for early January," one UN diplomat told AFP on condition of anonymity.
"It may slip into January but it will be announced," added a second UN diplomat.
Diplomats from all the governments involved in preparations have warned that events in Syria could still upset the planned conference.
Following past postponements, the UN has avoided expressing any optimism about the chances of calling a conference this time.
Signup to our newsletter and follow us on Facebook and Twitter!
"The point of the meeting on Monday is to take stock of where we stand. We'll see at that point what we can say about arrangements," UN deputy spokesman Farhan Haq told reporters on Friday.
Russia and the United States have been pressing since May for a followup to a Geneva meeting in June 2012, when the major powers agreed a declaration calling for a transitional government in Syria.
Russia, President Bashar al-Assad's key ally, has been pressing the government to cooperate on the conference. The United States, Britain and France have been working on the fractured Syrian opposition.
The followup, widely named Geneva II, would concentrate on how the transition can be established.
The Syrian National Coalition has agreed to go to a peace conference. It said that a delegation has gone to Geneva for talks with Brahimi ahead of Monday's meeting.
But its authority is threatened by Islamic and other militant groups and a coalition demand that Assad stand down is one reason Geneva II is unlikely to halt a war which the UN says has left well over 100,000 dead.
The Syrian government, in turn, has insisted that Assad's future cannot be discussed. "There are still doubts over whether Assad will send a delegation to Geneva that can take decisions," commented a UN diplomat.
Brahimi and the United States and Russia also face obstacles over how to get Iran, an Assad backer, and Saudi Arabia, a major supporter of the opposition, involved.
Iran has yet to accept the Geneva declaration of 2012, and western nations say it should not be involved in peace talks until it does.
"The compromise may be that Iran and Saudi Arabia will take part in meetings around the conference, but not the formal talks," said a senior Western official.