GENEVA — The main Syrian opposition bloc said Thursday — the day before United Nations-brokered peace talks were to start in Geneva — that it was still not sure whether it would send a delegation, raising new doubts about whether the meetings would be held.
A spokesman for the group said it wanted an assurance from Secretary-General Ban Ki-moon that the Syrian government would lift its sieges of rebel-held towns.
The statement was the latest in a series of maneuvers highlighting the opposition bloc’s reluctance to take part in talks while its fighters, and the civilians behind their lines, are under mounting pressure from Syrian government forces.
The bloc, known as the High Negotiations Committee, is backed by Saudi Arabia and includes a variety of opposition groups and dissident politicians. But it excludes some major combatants, including the Islamic State militant group and the Nusra Front, an affiliate of Al Qaeda.
The committee’s hesitation suggests that the modest expectations for the talks may have to be lowered further. The opposition’s focus now is on getting the sieges lifted, so that it can show some concrete gain from the peace effort.
“We are willing to go, we are willing to participate, but at least these humanitarian issues should be solved,’’ Salem al-Meslet, a spokesman for the bloc, said by telephone from Riyadh, the Saudi capital, where the committee has been meeting.
The demand from the High Negotiations Committee is meant to put pressure on the government of President Bashar Assad of Syria, through its ally Russia, a veto-wielding member of the Security Council.
Diplomats said Thursday that they expected the bloc to send a small group of leaders to Geneva, if only to meet with the UN mediator, Staffan de Mistura — and of course, to broadcast their message to the journalists assembled here.
Meslet said his group would make a final decision only after hearing directly from Ban. “At least we want to hear a promise, something to encourage us,’’ he said.
The United Nations has said that 18 towns — with about 400,000 people — are cut off from deliveries of food and medicine. One town, Deir al-Zour, accounts for half of those people; it is besieged by Islamic State militants, with whom there are no negotiations. But by the United Nations’ reckoning, most of the rest are in towns besieged by government forces.
Ban has warned that using starvation as a weapon is a war crime. The Security Council has called for all the sieges to be lifted in compliance with international law.
The talks were arranged under a binding Security Council resolution that senior US and Russian officials invested a great deal of diplomatic energy into drafting and adopting. UN diplomats said the talks would still go ahead on Friday.
The talks are being carefully choreographed to try to avert failure. They are not meant to be face-to-face negotiations, at least to start; instead, government and opposition delegations are to gather in separate rooms at the UN compound in Geneva.
