Delegations from Russia, Iran, Syrian government and invited United Nations officials have already arrived in Astana for talks about Syrian conflict scheduled to take place on Thursday.
Kazakhstan has invited Syrian rebels and government officials to peace talks on Wednesday and Thursday in Astana, after a first round last month organised by regime backers Russian Federation and Iran and rebel ally Turkey.
"Meetings have already begun, including with the participation of the armed opposition", he said.
The first round of talks on Syria that took place in Astana last month did not result in any significant breakthrough.
Mohammad Alloush, a rebel leader who is representing the opposition at talks this week in Kazakhstan, said he will insist on discussing the December 30 cease-fire.
A new Syrian constitution was not discussed at talks in the Kazakh capital of Astana on February 16, the head of Syria's government delegation has said.
Delegations of the Damascus government and the rebels who attended the January round of Astana talks refused to negotiate directly with each other or to sign any documents at the time.
In addition, U.N. Special Envoy Staffan de Mistura has been invited in his capacity as mediator of the Geneva peace talks, and the USA has been invited to participate as an observer.
A new round of UN-backed peace talks is due to begin in Geneva next week.
Russian Federation has billed talks in Astana as a prelude to Geneva, despite speculation that it was trying to sideline the West with the latest initiative.
The HNC touted the delegation as "unified" and said it includes representatives from two rival opposition groupings known informally as the Cairo and Moscow groups.
The opposition insists he must step aside, but his government says his future is not a topic for negotiations.
The first round of the discussions, which was similarly mediated by Tehran, Moscow and Ankara, took place in January and brought together representatives from the Damascus government and opposition groups for the first time during almost six years of conflict.