Secretary-General Ban Ki-moon Monday said that he would convene in Geneva on 22 January the long-sought international conference on Syria bringing together the Government and the opposition to a negotiating table for the first time since the conflict started in March 2011.

"This is a mission of hope," Mr. Ban said addressing journalists at the United Nations Headquarters in New York.

Mr. Ban called the upcoming conference, known as "Geneva II", a "vehicle for a peaceful transition" that fulfills the legitimate aspirations of all the Syrian people for freedom and dignity, and which guarantees safety and protection to all communities in Syria.

The goal of Geneva II would be to achieve a political solution to the conflict through a comprehensive agreement between the Government and the opposition for the full implementation of the Geneva communiqué, adopted after the first international meeting on the issue on 30 June 2012.

The communiqué, which has been endorsed by the UN Security Council, lays out key steps in a process to end the violence. Among these, the establishment - based on mutual consent - of a transitional governing body with full executive powers, including over military and security entities.

"I expect all partners and parties to demonstrate their support for constructive negotiations," Mr. Ban said. "All must show vision and leadership."

He added that it would be "unforgiveable" not to seize this opportunity and reiterated that the conflict remains "the world's greatest threat to peace and security" which can only be solved through political means.

The fighting has killed more than 100,000, driven almost nine million from their homes, left countless missing and detained, and terrible violations of human rights, Mr. Ban said.

In addition, it continues to send tremors through the region and has forced unacceptable burdens on Syria's neighbors, he stressed.

Mr. Ban urged all parties to begin working now and take steps to help the conference succeed, "including toward the cessation of violence, humanitarian access, release of detainees and return of Syrian refugees and internally displaced to their homes".

The UN chief expressed his "profound gratitude" to the initiating states, the Governments of Russia and the United States, as well as to other Member States and to the Joint Special Representative of the UN and the League of Arab States, Lakhdar Brahimi.

Speaking to the press from Geneva, Mr. Brahimi echoed the Secretary-General's call for action now to end the conflict. "We very strongly appeal to the Syrian Government and the opposition not to wait for the conference, to [take] some confidence-building measures, diminish the violence, release prisoners and detainees of all sorts."

As for the conference itself, he said that while the list of invitees was being finalized – telling reporters that Iran and Saudi Arabia would be among the possible participating delegations – the UN was asking both Damascus and the opposition to name their delegations as soon as possible. "This conference is really for the Syrians to come to Geneva and talk to one another and, hopefully, start a credible, workable, effective peace process for their country."

What Mr. Brahimi could confirm was that the National Coalition will play a very important role in forming the [opposition] delegation. "Not all the people who want to come to Geneva will be able to come but they should know that this is not an event, this is a process," he said, adding that all those wishing to participate in rebuilding "the new republic of Syria will be able to do so in the course of the process."