The main Syrian opposition delegation vowed Saturday not to participate in U.N.-sponsored peace talks with the government unless their demands are met, including lifting the siege imposed on rebel-held areas and an end to Russian and Syrian bombardment of regions controlled by opposition fighters.

The oppositions warned that if these conditions are not met, there will be no reason for the team to stay in Geneva.

The nearly five-year conflict has left at least 250,000 people dead, forced millions to flee the country and given an opening to the Islamic State group to capture territory in Syria and Iraq. It has drawn in U.S. and Russia, as well as regional powers such as Turkey, Saudi Arabia and Iran

The indirect peace talks began here Friday with a meeting between the United Nations envoy and the Syrian government delegation. The main opposition group, the Higher Negotiations Committee or HNC, boycotted that session saying it won't take part until a set of preliminary demands are met: releasing detainees, ending the bombardment of civilians by Russian and Syrian forces, and lifting government blockades on rebel-held areas.

The HNC later agreed to send a delegation to meet with U.N. officials, while still insisting it would not negotiate until their demands are met. The HNC decision to come to Geneva gave a glimmer of hope that peace efforts in Syria might actually get off the ground for the first time since two earlier rounds of negotiations collapsed in 2014.

"We are here to discuss humanitarian matters first and if this happens we will start the negotiations," the opposition's delegation chief spokesman Salem al-Mislet told reporters upon the arrival of some two dozen members at their hotel in Geneva. "If not, there will be no negotiations and there will be no reason for us to stay here."

He added that the HNC team will discuss these issues with U.N. Special Envoy to Syria Staffan de Mistura during a meeting scheduled for Sunday.

"We are keen to make this negotiation a success but you should ask the other side. The other side is pretending to present the Syrian people. In fact he is killing the Syrian people. We're here to save the remaining children of Syria," al-Mislet said in English.

Another senior delegation member, Riad Naasan Agha, said their team includes several rebel groups including the Army of Islam that controls large areas near the capital Damascus. Asked if the ultraconservative Ahrar al-Sham group is part of the team, he said "they did not withdraw (from the HNC) but they are not with us" in Geneva.

The meetings in Geneva, billed as multiparty talks, are part of a process outlined in a U.N. resolution last month that envisions an 18-month timetable for a political transition in Syria, including the drafting of a new constitution and elections.

"When there is an order for a cease fire against civilians, an order to lift the siege and an order to release detainees then we will enter the negotiations and talk about a transitional governing body with full executive powers," he said.

The Syrian opposition team is demanding that a governing body with full executive powers rules Syria during the transitional period. They say President Bashar Assad should not have any role during the transitional period.

Meanwhile, officials from Syria's largest Kurdish group left Geneva on Saturday after being excluded from the negotiations, a Kurdish official and opposition figures said.

Saleh Muslim, co-president of the Democratic Union Party, or PYD, left when it became clear he would not be invited to participate, according to Kurdish official Nawaf Khalil.

The participation of the PYD has been a divisive issue in advance of the Geneva talks. Turkey, which has struggled with its own large Kurdish population, considers the PYD a terrorist organization and the HNC claims they are too close to the Syrian government.

Unlike other groups from outside the HNC that were invited as advisers, the PYD received no invitation from U.N. Special Envoy to Syria Staffan de Mistura.

The move to exclude the PYD angered Qadri Jamil, a former Syrian deputy prime minister who has become a leading opposition figure but is not part of the HNC. Jamil said the PYD's military wing has been the most effective force on the ground in Syria fighting the Islamic State group.

"The PYD is a historic part of the Syrian democratic opposition and PYD today is fighting terrorism on the ground and it is a main force," Jamil told a group of journalists in Geneva on Saturday.

Jamil said they are working with the U.N. to resolve the crisis regarding the representation of the PYD.

Bassam Bitar of the opposition's Movement for a Pluralistic Society said the PYD will most likely be invited to take part in future rounds of negotiations.