The UN-backed Syrian peace talks restarted in Geneva on Tuesday without the regime delegation after the Syrian government team left last week without confirming it would return.
De Mistura said the Syrian government had informed him Thursday that the delegation will return to Geneva to participate in the talks aimed at bringing about peace after seven years of bloody conflict in Syria.
The negotiations' "four baskets" - a new constitution, governance, elections and combating terrorism - have been discussed, as well as issues such as detainees, abductees, missing persons and humanitarian access. The second basket, which includes post-war elections, is supposed to be discussed at a ninth round of talks.
The regime delegation blamed its departure on what it considers the opposition's uncompromising stance on Assad's future. "This is in the context of the constitution and electoral processes". The unified opposition accepted the offer but the regime delegation refused. "On the contrary, they are willing to undermine any track that might lead to a political solution", Mr Aridi said.
France accused the Syrian regime on Wednesday of obstructing the peace talks with its refusal to return to Geneva and called on Damascus' ally Russian Federation not to shirk its responsibility to get the regime back to the negotiating table.
"This refusal highlights the obstruction strategy of the political process carried out by the Damascus regime, which is responsible for the absence of progress in the negotiations", French foreign ministry deputy spokesman Alexandre Georgini told reporters.
The government delegation led by head of Syria's mission to UN, Bashar al-Ja'afari, left the talks on Saturday for a weekend break and did not return on Tuesday, the day set by UN to resume the talks.
He also said that Russian Federation, as one of Assad's main supporters, needed to assume its responsibilities so that the Syrian government finally entered the negotiations.
During last week's sessions, de Mistura shuttled between the representatives of the two warring sides, who did not meet face-to-face.
This was outlined earlier at the same briefing by the United Nations special advisor on humanitarian affairs Jan Egeland and de Mistura said it is "unacceptable".