Syrian peace talks could collapse before they even start, with the main opposition coalition bloc issuing a deadline for the withdrawal of Iran's invitation to the talks.

The Syrian National Coalition, a key player in this Wednesday's Geneva II meeting, has given a deadline of Monday night for Tehran's invitation to be rescinded. It is furious about the United Nations' overtures to Iran, which is an ally of President Bashar al-Assad.

Anas Abdah, a member of the Coalition's political committee, told Reuters: "We are giving a deadline of 19:00 GMT for the invitation to be withdrawn."

Earlier on Monday, Abdah told Al Jazeera by phone that the bloc was "surprised" by UN Secretary-General Ban Ki-moon's invitation, saying: "It is illogical and we cannot in any way accept it."

"The Syrian Coalition announces that they will withdraw their attendance in Geneva II unless Ban Ki-moon retracts Iran's invitation," it said in a Twitter post quoting Louay Safi, the Coalition's spokesman.

Ban said Iran's Foreign Minister Mohammad Javad Zarif had promised his country would play a "positive and constructive role" if it were asked to participate.

"He has assured me that, like all the other countries invited to the opening-day discussions in Montreux, Iran understands that the basis of the talks is the full implementation of the 30 June, 2012, Geneva communique," he said.

However, Iran's Press TV reported on Monday that Tehran would participate in the upcoming Geneva II conference on the Syria crisis without accepting crucial elements of the 2012 Geneva communiqué, citing Chairman of the National Security and Foreign Policy Committee of Iran’s Majlis, Alaeddin Boroujerdi.

Iran has said it will attend the talks but it has not agreed to preconditions, which means there is no requirement for Assad to be removed from power and that a transitional government be established with full executive powers. It does, however, agree that a ceasfire is necessary.

'Unqualifed to attend'

Saudi Arabia, which backs Syrian opposition forces, has also rejected Iran's participation in Geneva II.

On Monday in an official statement it said that Iran did not "announce officially and openly its agreement [to]... the creation of a transitional government" and that this position rendered Tehran "unqualified to attend."

The disputes and threats regarding attendance come as Assad said he was likely to run in June's presidential race.

The Syrian president said on Sunday there was a "significant chance" he would make a candidacy bid.

"I see no reason why I shouldn't stand," he said. "If there is public opinion in favour of my candidacy, I will not hesitate for a second to run for election."

His statement further undermines a successful outcome for Geneva II. The Wednesday summit is meant to build on the Geneva I, which made no mention of Assad's departure.

The Swiss meeting is backed by both the United States, which supports the rebels, and Russia, an Assad ally.

"The Geneva conference must lead to clear results regarding the fight against terrorism," Assad said in an interview with the AFP news agency.

"That would be the most important result of the conference. Any political result that did not include the fight against terrorism would have no value," said Assad, who is embroiled in an almost three-year-old war with rebels fighting to topple him.

'Totally unrealistic'

Assad also ruled out that the Istanbul-based Syrian National Coalition to be given any ministerial positions in a new government, calling it "totally unrealistic."

The US suggested on Sunday it could support Iran's participation if it explicitly declares its support of a June 2012 plan for a political transition, meaning Assad would have to step down.

"This is something Iran has never done publicly and something we have long made clear is required," Jen Psaki, State Department spokeswoman, said in a statement.

"If Iran does not fully and publicly accept the Geneva communique, the invitation must be rescinded."

Syrian opposition groups and the US, which accuse Iran of supporting Assad with manpower and arms during the conflict, have long had reservations about the participation of Iran, although Ban and the UN special envoy on Syria, Lakhdar Brahimi, are backing Iran's involvement.