They want prisoners freed and aid efforts supported before they’ll decide about attending peace talks.

Syria’s main Western-backed opposition group pushed Tuesday for President Bashar Assad’s government to establish humanitarian corridors to besieged opposition areas and release political prisoners, saying it wants to see progress on those confidence-building measures before it will decide whether to attend an international peace conference.

The statement from the Syrian National Coalition made clear the huge hurdles still ahead as the international community tries to bring the warring sides together for peace talks scheduled for Jan. 22. The long-delayed negotiations, which would be the first face-to-face meeting between the Assad government and its opponents, aim to broker a political resolution to Syria’s civil war.

After months of diplomacy, the U.N. announced the date for the peace conference on Monday, raising hopes that an end to the seemingly intractable conflict could be within reach. A full list of participants has not been set yet.

The violence, however, has shown no sign of tapering off. On Tuesday, a suicide car bombing outside a bus station in the town of Sumariyah near Damascus killed at least 15 people and wounded more than 30, state TV and activists said.

Meanwhile, government air strikes on the rebel-held town of Nabek, where Assad’s troops are waging an offensive, killed at least seven people, the Britain-based Syrian Observatory for Human Rights said. The group monitors the conflict through a network of activists on the ground.

Speaking to reporters in Cairo, Coalition chief Ahmad al-Jarba said the opposition umbrella group “did not make a final decision” yet on attending the Geneva talks. He said his group has indicated its desire to take part, “but we think that the Syrian regime is the one which doesn’t want to go to Geneva 2 but the Russians are putting pressure on them to attend.”

Monzer Akbik, chief of staff of al-Jarba’s office, later said the coalition is ready to participate based on “positive signals” they have received on their demands for humanitarian corridors and the release of detainees.