UN Secretary General Ban Ki-moon described the conference – scheduled to take place on January 22 – as “a mission of hope”, however, many experts remain pessimistic that the talks will even take place.

“At long last and for the first time, the Syrian Government and opposition will meet at the negotiating table instead of the battlefield,” said Mr Ban in New York.

“The war continues to send tremors through the region and has forced unacceptable burdens on Syria’s neighbours.”

Mr Ban described the conflict as “the world’s biggest threat to international peace and security”. “It would be unforgivable not to seize this opportunity to bring an end to the suffering and destruction it has caused.”

However soon after the announcement, Laui Safi, a spokesman for the opposition Syrian National Coalition, said the group would only attend the meeting if the following preconditions were met: the release of prisoners and relief for besieged towns, and that President Bashar al-Assad plays no role in the transitional government.

The opposition will not only need to maintain unity within its own ranks but also ensure the support of all groups fighting inside Syria – including the Al-Qaeda linked jihadi groups – to ensure the talks went ahead, analysts said.

“The concern for the Opposition is that either they dissolve in disagreement or they are outmanoeuvred at the table by a Syrian regime that holds more cards at this point,” said Mona Yacoubian, a senior Middle East adviser at the Washington-based Stimson Centre.

“We see the regime gaining on the ground … they are playing a role with the implementation of the chemical weapons agreement which gives them the perception of a degree of authority, and their allies Russia and Iran are very strongly behind them in a way that is not the case with the Syrian opposition.”

There is not yet any detail on who will attend the talks – in the past there has been tension around whether Iran – a staunch ally of President Assad – or Saudi Arabia, the powerful Sunni backer of the Opposition, will have a seat at the table.

The US Secretary of State John Kerry, fresh from negotiating an interim deal with Iran on its nuclear program, acknowledged the difficult two months ahead between now and the scheduled talks.

“We are well aware that the obstacles on the road to a political solution are many, and we will enter the Geneva conference on Syria with our eyes wide open,” Mr Kerry said.

“To contain the growing threat from extremism and foreign fighters within Syria, and to ensure respect for Syria’s territorial sovereignty, we cannot delay the work of establishing a transitional government.”

It is unclear whether Sunday’s historic deal with Iran will have any sway over the talks, although Mr Kerry noted: “Foreign states have considerable influence on the factions waging war within Syria, they too have an important role to play.”

If the talks were to have any chance of success, they needed a strong regional coalition to back them, Ms Yacoubian said.

But after Sunday’s deal on Iran’s nuclear program – which has so angered Israel and the US’s key ally Saudi Arabia – such a coalition was less likely, she said.
“Saudi Arabia is going to be a critical challenge, precisely because the Saudis are now very distrustful of the US and what it is doing with Iran ... those concerns extend to Syria as well.”