The UN has withdrawn an invitation for Iran to the January 22 Geneva 2 peace conference after Syria’s main Western-backed opposition group threatened to pull out of talks if the Islamic Republic attends.

A UN spokesperson announced Monday that UN chief Ban Ki-moon has withdrawn his invitation for Iran.

"[Ban] continues to urge Iran to join the global consensus behind the Geneva communique," Ban's spokesman Martin Nesirky said. "Given that it has chosen to remain outside that basic understanding, [Ban] has decided that the one-day Montreux gathering will proceed without Iran's participation."

Following the announcement Syria’s main opposition group - Syrian National Coalition – has confirmed its participation in the peace talks.

"We appreciate the United Nations and [UN Secretary-General] Ban Ki-moon's understanding of our position. We think they have taken the right decision. Our participation is confirmed for 22 January," Monzer Akbik, chief of staff of the president of the National Coalition told Reuters.

Washington said it is hopeful that the sides can now refocus their efforts to end the Syrian civil war.

"We are hopeful that, in the wake of today's announcement, all parties can now return to focus on the task at hand, which is bringing an end to the suffering of the Syrian people and beginning a process toward a long overdue political transition," State Department spokeswoman Jen Psaki said in a statement.

Meanwhile the Iranian ambassador to the UN, Mohammad Khazaee, has expressed doubts that the Geneva 2 conference will settle the conflict in Syria. “I’m not very optimistic that the Geneva 2 conference might solve anything in Syria,” the diplomat told Itar-Tass on Monday.

Earlier on Monday, the Syrian National Coalition gave the UN until 1900 GMT to withdraw the invite that it sent to Tehran a day earlier and that was accepted by the Islamic Republic. Otherwise, the coalition said, it would boycott the meeting.

The opposition group said it would agree to Iran's participation only if it “publicly states that it is withdrawing its forces, committing to the Geneva 1 agreement in full and committing to implementing any results of Geneva 2,” Anas Abdah, a member of the Coalition's political committee, told Reuters earlier.

Iran is a key backer of Syrian President Bashar Assad and its attendance of the peace talks has been prompting heated debates throughout the preparation period.

Iran maintained it would take a seat at the talks only if no preconditions are set. Several other powers, including the US, insisted that Tehran should agree that the premise of the peace talks is to pave the way for establishing a transitional governing body in Syria, which would remove Assad from power.

Moscow has insisted on Iran’s participation in the talks and said that not inviting the republic would be “an unforgivable mistake.”

“Those who question such a need are clearly not interested in a fair resolution of the Syrian crisis,” Russia’s UN envoy Vitaly Churkin said at a Security Council meeting on Monday, cited Itar-Tass. He added that it would be “a big mistake” if the Coalition decided against joining in the Geneva 2 talks.

Sunday’s last-minute invite by UN chief Ban Ki-moon sparked a confrontation with Saudi Arabia, the US, the UK and France.

The American State Department said it would accept the invitation on the condition Iran expresses “explicit and public support for the full implementation of the Geneva communiqué including the establishment of a transitional governing body by mutual consent with full executive authorities.”

The Geneva communiqué outlines key steps and measures for a peaceful solution to the Syrian crisis. The document, which was agreed upon at the first Syrian peace conference in June 2012, proposed a transitional government to be elected by mutual consent between the Assad government and the opposition. It was vague on the fate of the Syrian president.

Ban said that Iranian Foreign Minister Mohammad Javad Zarif had assured him that Tehran understands the basis of the talks is the full implementation of the Geneva peace plan.

However, Iran's deputy foreign minister Hosein Amirabdollahian voiced a different position on Monday.

“Setting such a condition to accept the Geneva 1 agreement for attending the Geneva 2 meeting is rejected and unacceptable,” he said, as cited by ISNA news agency. “Iran will attend the talks without any precondition, based on an invitation by UN Secretary-General Ban Ki-moon.”