A long-awaited peace conference on Syria is likely to go ahead without one of the major participants of the conflict after the United Nations withdrew an invitation to Iran to attend the talks in Geneva.
The UN Secretary-General, Ban Ki-moon, rescinded Iran's invitation on the same day it was unexpectedly issued, following the threat of a boycott from the Syrian opposition and pressure from the United States.
That the conference would take place at all looked in serious doubt through much of Monday, with Iran's participation being a major sticking point for the opposition.
The meeting, arranged with strong US and Russian backing, is the only opportunity available for de-escalating, if not ending, the civil war in Syria.
Iran is a main backer of President Bashar al-Assad and has supplied him with arms, money and military advisers during the three-year-old conflict. Critics argue that holding a peace conference with some main regional players, such as Saudi Arabia, but not others, like Iran, is unrealistic and would limit chances of achieving peace.
The invitation to Iran to attend the Geneva II meeting came from Mr Ban and did not appear to have been expected by American officials. Mr Ban had earlier argued that a successful conference "needs all players at the table" and said that the Iranian Foreign Minister Javad Zarif had assured him that Iran accepted that "the goal of the negotiations is to establish by mutual consent a transitional governing body with a full executive powers".
The Syrian Opposition Coalition (SOC), the exiled opposition political grouping that narrowly decided over the weekend to attend the talks, expressed its shock at the invitation to Iran. The Western and Gulf-backed political arm of the rebels, which is the only part of the opposition planning to go to Switzerland, threatened to pull out if Iran was to attend. Its spokesman, Louay Safi, said that "the Syrian Coalition will withdraw their attendance in Geneva II unless Ban Ki-moon retracts Iran's invitation."
The UN later announced that urgent discussions were under way to ensure the talks went ahead. Later, when public statements from Iran made clear that it did not agree to preconditions for the talks, a spokesman for the Secretary-General announced that the conference would proceed without Iran's participation.
Russia says there would be little point in holding a conference without Iran present. The Russian Foreign Minister Sergei Lavrov said that "not to ensure that all those who may directly influence the situation are present would, I think, be an unforgivable mistake".
The chaotic diplomacy that followed Iran's invitation and subsequent withdrawal from the talks within the space of a day appears have been caused by a supposition that the terms under which the conference is held are less woolly and ambiguous than they are.
The US and Russia have always disagreed since the first Geneva meeting in June 2012 about whether the departure of Mr Assad was an immediate aim or an ultimate long-term goal. In practice, since he controls almost all Syrian cities and his forces are advancing, albeit slowly, it is unlikely that Mr Assad would agree to step down or even seriously share power with the opposition. This was underlined when Mr Assad said in an interview yesterday that he might seek re-election later this year.
It is surprising that a diplomat as cautious as Mr Ban would not have cleared his offer to Iran with American officials at a senior level. A UN invitation would have freed the US of the embarrassment of issuing an invitation itself. Already, in insisting that the conference take place, the US and Russia have shown a determination to bring the war to an end which has not previously been in evidence. The new mood of co-operation between the two countries stems from their joint success in removing Syria's chemical weapons peacefully after the US and Britain came close to launching air strikes last September in retaliation for poison-gas attacks in Damascus. The Syrian civil war involves many other outside players, notably Saudi Arabia and Iran, which have been locked in confrontation since the overthrow of the Shah of Iran in 1979.
Syria has also become the battleground for a deepening religious war between Sunni and Shia that is spilling out into Iraq and Lebanon. Saudi Arabia and Qatar are more determined to see the civil war end with the defeat of Mr Assad than are the US and West Europeans who are increasingly fearful of the expansion of jihadi Islam and the growing strength of al-Qa'ida-type movements in Syria and Iraq. Americans were particularly shaken to see the Islamic State of Iraq and the Levant (Isis) once more take control of Fallujah, 40 miles west of Baghdad, from which they were driven in a battle by the US Marines in 2004.
Meanwhile, in Damascus Mr Assad sounded confident in an interview with AFP, saying: "I see no reason why I shouldn't stand [in a presidential election this year]. If there is public desire and a public opinion in favour of my candidacy, "I will not hesitate for a second to run for election." He added that having members of opposition in his government was "not realistic" and that the talks in Switzerland should focus on fighting terrorism.
Mr Assad may be overconfident because political and military developments have been running in his favour. The opposition is not only split but is fighting a savage "civil war within the civil war" in which over 1,000 rebels were killed in the first two weeks of the year. But the military stalemate on the ground remains very much where it was since last summer and the government has failed to capture rebel-held districts in Damascus. The long-term future of Syria is one of geographical division with each side holding on to well-defended enclaves.
The Geneva II negotiations were never expected to end the war in Syria, but they might de-escalate it significantly through local ceasefires and humanitarian assistance to besieged areas. These have often collapsed in the past but might be more stable under greater international scrutiny. If even a small section of the opposition does turn up in Geneva then its presence validates for the first time negotiations between the warring parties that have hitherto simply wanted to eliminate each other.
The complexity of the Syrian war that has drawn in so many foreign players and become the focus of so many other conflicts - such as Saudi Arabia and Qatar vs Iran, Sunni vs Shia, the US and Israel vs Iran and the US against Russia - that it will be difficult to end. But there are some signs that the political temperature in the region is dropping. Turkish President Abdullah Gul has called for a "recalibration" of Turkey's hostile policy towards Syria where it has done all it can to help the rebels overthrow Mr Assad but without success. The open 500-mile-long border between Turkey and Syria has been crucial to the success of the rebels in the north of the country. Turkey is therefore in a strong position to mediate or force concessions from both sides if it takes a more evenly balanced position. It is also seeking to improve its relations with Iran.
A further incentive for Turkey and others - such as state and private donors supporting rebels in the Gulf - to think about bringing an end to the conflict is the apparent success of Isis in counter-attacking other rebel groups that seemed to be making headway against it a fortnight ago. Isis has recaptured Raqqa, the one provincial capital held by the rebels, and taken important towns on the border with Turkey. Powerful rebel groups like the Islamic Front, reported to be funded by Saudi Arabia, have failed to make any decisive headway against Isis. This puts in doubt Saudi hopes of establishing an Islamic military force capable of defeating both Mr Assad and al-Qa'ida.
The fate of the Geneva II conference is still in doubt, but several powerful participants in the Syrian war have an interest in bringing it to a conclusion or at least ensuring that it does not spread further. The endgame may not be yet at hand but opportunities for de-escalation are greater than ever before.
Syria conflict: the key players
Syrian regime
Speaking on Monday, President Bashar al-Assad reiterated that he does not intend to step down and would not share power with the SOC.
After Washington's decision to abandon air strikes against regime targets, pro-Assad forces have made considerable gains on the battlefield. Regime representatives said they would attend the talks.
Syrian Opposition Coalition (SOC)
The SOC is the main political opposition to Assad. Based in Istanbul, the coalition is backed by the West, but has struggled to win the support of rebel fighters in Syria, who view its members as detached from the conflict and consumed with infighting. The SOC voted to attend talks in Geneva on the condition that the primary aim would be the formation of a transitional government and that Assad would have to step down.
The rebels
The myriad rebel groups fighting against Assad's forces possess many different ideologies, but most are opposed to peace talks in Geneva. They say victory can only be won on the ground and that Assad's government cannot be trusted in talks.
Iran
Assad's main foreign backer has previously been excluded from talks. The US and France said yesterday, before Iran's invitation was rescinded, that Iran would not be welcome unless it publicly backed the 2012 Geneva accord, which calls for the formation of a transitional government in Syria.
The West
Western countries have stuck to the demand that Assad must leave power. But given the regime gains on the ground and in the diplomatic arena, this has become far less realistic since Geneva I.
Saudi Arabia and Qatar
While the West has refused to support the rebels militarily, that gap has been filled by Saudi Arabia and Qatar. The vast majority of funding to the rebels is thought to come from the two Gulf countries - with much of it flowing to Islamist groups. Saudi Arabia is thought to be the principal backer of Syria's largest rebel coalition, the Islamic Front.
Hezbollah
The Lebanese militant group has sent thousands of fighters to support Assad - a key backer of the group. Hezbollah leader Hassan Nasrallah views the fight in Syria as a threat to his party and to the region.
Russia
Russia has been a key backer of Assad throughout the conflict - both financially and materially - and has repeatedly vetoed any attempts to pass UN resolutions condemning the Syrian regime. Russia strongly opposes Assad's removal.