Syria's opposition on Sunday announced its 21-member delegation, including 10 rebel representatives, for a new round of UN-sponsored peace talks in Geneva scheduled for February 20.

The delegation will be headed by Nasr al-Hariri, a member of the National Coalition, replacing Assad al-Zoabi, who led the opposition at several previous rounds of talks in Geneva last year.

The delegation's chief negotiator was named as Mohamed Sabra, a lawyer who was part of the opposition's technical team during negotiations in Geneva in 2014.

He replaces Mohamad Alloush, a rebel from the powerful Army of Islam faction.

Alloush served as negotiator during three rounds of peace talks in Geneva as well as negotiations in the Kazakh capital Astana in January organised by Turkey and Russia.

Neither Alloush nor the Army of Islam were listed as members of the delegation to Geneva, though it was unclear if the group was boycotting the talks or would be represented by other delegates.

No reason was given for the decision to replace either Zoabi or Alloush.

The delegation includes representatives from several rebel groups, including Faylaq al-Sham, an Islamist faction active around Damascus, and Liwa Sultan Murad, a battalion close to Turkey.

The umbrella High Negotiations Committee (HNC) opposition group said the delegation to the talks would for the first time include representatives from two additional opposition groupings, known informally as the Moscow group and the Cairo group.

But representatives from both groups denied they were included in the delegation.

In the past, the HNC has opposed including the two rival opposition groupings in its delegation, accusing members of the coalitions of being too flexible with regard to the Syrian government.

The Moscow grouping includes former minister Qadri Jamil, and is close to the Russian leadership, while the Cairo grouping includes former foreign ministry spokesman Jihad Makdissi.

Invitations to the talks in Geneva have yet to go out, having been delayed in part to allow the opposition to decide on the composition of their delegation.

UN envoy Staffan de Mistura warned last week that he would pick the opposition delegates to the talks if they could not decide on time.

But he later appeared to backtrack and said he would delay dispatching invites.

Ahead of the talks, Kazakhstan has invited Syrian rebels and government officials back to Astana on February 15-16, but neither party has said officially yet if they will attend.

De Mistura will not attend the Astana meeting, but will send a "technical team," his spokeswoman said.