The Syrian opposition says it will not be at peace talks scheduled to begin in Geneva on Friday.
The main opposition delegation, a Saudi-backed group known as the High Negotiations Committee, said Thursday that responses it had received to its demands for an end to airstrikes and the lifting of a siege in Syria were not acceptable.
The committee has been meeting in Riyadh this week, and members said they would remain there through Friday, missing the start of the proximity talks in Switzerland.
Representatives, however, did not rule out participating later in the talks, which are expected to last for months.
The announcement reflected the difficulties in setting the stage for negotiations to end a conflict that will soon enter its sixth year. That conflict has killed a quarter-million people and has displaced nearly 4.6 million others.
Staffan de Mistura, the U.N. special envoy for Syria, said in a video message Thursday that the talks could not be allowed to fail. “This conference must be an opportunity not to be missed," he said.
U.N. organizers said the meetings set to start Friday would not be peace negotiations, but proximity talks meant to lay the groundwork for negotiations.
Syrian government representatives decided to attend after discussions with de Mistura earlier this month in Damascus.
Despite continuing attacks by both the Russian-backed Syrian government and a fractured opposition that includes al-Qaida and Islamic State terrorists, the U.N. envoy sees the talks as an important first step. “My job is to be always optimistic,” he said after his recent meetings with officials of President Bashar al-Assad's government.
De Mistura sent out invitations to the talks Tuesday. U.N. officials indicated the list would not be made public until the talks had begun.
The talks will get under way against a backdrop of ongoing violence. Syrian forces loyal to Assad have intensified their bombing campaigns, as have Russian warplanes.
At the same time, Islamic State militants have not ceased their attacks. The group claimed responsibility for two bombs Tuesday that killed 22 people in Homs, an opposition stronghold.
Once talks start in Geneva, the plan is to keep all parties in separate rooms, with no face-to-face meetings.
David Butter, a Middle East politics expert at Chatham House in London, said the talks might serve as a needed sign that the world community is doing something to try to stop a seemingly endless and profoundly destabilizing conflict.
“This is a realistic appraisal of international consensus that we need to have some sort of political process going on — perhaps a recognition of the parties, certainly the opposition parties, that they’re starting to get exhausted with the conflict itself, and it has been so damaging on every level, humanitarian and otherwise,” Butter said.
Pressure to enter into negotiations is largely external, with the United States, the European Union, Russia, Turkey and Saudi Arabia all pushing for a solution.
In the West, that urgency has been fueled by terrorist attacks in Paris and the United States, and by the migrant crisis. The number of migrants flowing mainly from Syria and Iraq to Western Europe is expected to reach 4 million by the end of next year. Officials say nearly 40,000 have entered Western Europe in the three weeks since the start of 2016.
The Syrian talks had been set to begin January 25 but were delayed to Friday by discussions about who should represent the opposition.