Ahmad Jarba, the leader of Syria’s opposition National Coalition, said Sunday that the US-led “Friends of Syria” grouping had agreed that President Bashar al-Assad and his family will have no role in the country’s future.

Jarba did not announce whether or not the opposition would take part in peace talks with representatives of Assad’s regime due to start next week in Switzerland. The Coalition, which is under intense pressure to confirm its participation, has said it will decide on the issue on January 17.

Western powers on Sunday stepped up their pressure on Syria’s divided opposition to enter talks with President Bashar al-Assad’s regime at the start of a new round of diplomatic efforts to end the country’s civil war.

US Secretary of State John Kerry joined ministers from 10 other countries at a Paris meeting aimed at persuading the opposition National Coalition to attend a first round of talks scheduled for Montreux, Switzerland on January 22.

The Swiss talks have been organised in an attempt to revive a long-stalled framework for peace involving a cessation of hostilities and the creation of a national transitional government that could involve figures from the current regime and the opposition. But opposition leaders are wary of being drawn into a process they fear could result in Assad clinging on to power and have yet to give a commitment to attending.

Coalition leader Ahmad Jarba has called for Assad to stop using heavy weapons, lift sieges on a number of opposition-held areas and allow the opening of humanitarian corridors as a show of good faith ahead of any talks.

There has been no sign of progress on those issues but US officials have expressed confidence that, with little prospect of securing a military victory after nearly three years of fighting, the opposition will come to Montreux.

“I think in the final analysis they won’t want to miss that opportunity, because frankly there’s no other game, really,” a US diplomat told reporters.

British Foreign Secretary William Hague said it was in the opposition’s interests to attend the talks and try to end a conflict that has caused 130,000 deaths and created more than two million refugees. “In the end, there’s got to be a political solution in Syria,” Hague told Sky News from Paris. “This is going to put the Assad regime on the spot if everybody turns up at those peace talks.”

German Foreign Minister Frank-Walter Steinmeier echoed Hague’s remarks. “I know that it is not an easy decision for the opposition in Syria,” he said. “We want to work to convince them today in Paris and remove the last obstacles that may arise. “We must get down to work in earnest. I fear that we will not be successful if we do not manage to include the opposition in these talks.”

The balance of power in the conflict in Syria appears to have tipped in Assad’s favour over the last week as deadly clashes have erupted between the mainstream opposition and an Al Qaeda-linked group, the Islamic State of Iraq and the Levant (ISIL), with which they were previously allied.

According to NGOs monitoring the conflict, at least 700 people have been killed since the fighting started January 3 and the ISIL is threatening to abandon frontline positions in the area around Syria’s second city, Aleppo.  The fighting has exacerbated concern in western capitals over the strength of radical groups within the broad alliance of forces fighting Assad. Hopes of progress towards peace in Syria rose last year when Assad agreed to give up the regime’s chemical weapons after the West pulled back from the brink of threatened military intervention.

Opposition leaders fear that deal, which involved Syria’s ally Russia becoming a pivotal player in the efforts to end the conflict, has diluted the West’s determination to see Assad removed from power.

Among the other issues due to be discussed on Sunday was whether Iran, an important backer of Assad, will have any role in peace talks further down the line.

Russia has been lobbying for Tehran to be brought into the process and the issue is likely to dominate discussions on Monday between Kerry, his Russian counterpart Sergei Lavrov and Lakhdar Brahimi, the UN-Arab League special envoy to Syria.