Assad in the Hague? UN to gather war-crime evidence
The announcement follows December's vote by the General Assembly in favour of establishing the mechanism.
"We expect to start very, very shortly with just a handful of people," a UN human rights official told Reuters.
She added that the team will "analyse information, organise and prepare files on the worst abuses that amount to international crimes - primarily war crimes, crimes against humanity and genocide - and identify those responsible".
UN Secretary-General Antonio Guterres is expected to name the team's head later this month.
Lacking powers of prosecution, however, the team will only be able to prepare files for potential use in future cases brought brought forth by states or the International Criminal Court in the Hague against the Syrian regime and warlords.
Similarly, the UN's Commission of Inquiry set up in 2011 lacked a prosecution mandate, despite issuing 20 reports accusing the Syrian government, rebel forces and the Islamic State group of mass killings, disappearances, rapes and using child soldiers.
It denounced the Assad regime for employing methods amounting to "extermination" and also compiled a secret list of a number of suspects on all sides.
According to a report by Amnesty International last week, the Syrian regime has carried out mass hangings that have resulted in the deaths of up to 13,000 prisoners.
Syria's government were swift in rebuking the accusation, saying that the report was "devoid of truth".
The new fact-finding team will require a start-up budget of between $4-6 million, a UN report from January said. Although $1.8 million has been raised so far, contributions to the fund are voluntary, causing an obstacle to getting the project moving, a UN official said.
Experts in investigations, prosecutions, military and forensics will be among the team of 40-60 recruited by the UN, diplomats said.