De Mistura told reporters that the start date was pushed back because of a “stalemate” over the makeup of the delegations, but that the invitations to the participants were expected to be sent out on Jan. 26.
“We are going to aim at proximity talks starting on the 29th and ongoing for six months. There will be no opening ceremony” De Mistura said, adding that the first round was expected to last between two to three weeks.
Securing a cease-fire and space to deliver humanitarian aid to suffering Syrians will be among the first priorities, he added. “We are all feeling... the time has come to at least try hard to at least produce an outcome,” De Mistura told reporters.
The talks will mark the first time the warring sides will take part in negotiations since January 2014, when de Mistura's predecessor, Lakhdar Brahimi, hosted high-level but fruitless meetings in the Swiss cities of Montreux and Geneva, a round of talks known as Geneva II.
Peace talks meant to begin this week were stalled partly over the question of who would represent the opponents of Syrian President Bashar al-Assad.
Earlier in the day, U.S. Secretary of State John Kerry phoned his Russian counterpart, Sergei Lavrov, to discuss the planned negotiations, after piling pressure on Syrian opposition figures to attend.
Russia's Foreign Ministry said in a statement that the two diplomats “called on … de Mistura to set a date for negotiations between Syrians as quickly as possible.”
The talks are part of a U.N.-backed plan agreed last year that envisaged negotiations, followed by the creation of a transitional government, a new constitution, and elections within 18 months.
A few hours before the Russian Foreign Ministry's statement, Kerry said in Laos that he hoped for “clarity” within 48 hours on talks.
Kerry said he had held a flurry of conversations with key parties including his French, Turkish, Russian and Saudi counterparts to try to get the talks to the starting line.