The Friends of Syria, an alliance of mainly Western and Gulf Arab countries who support the Syrian opposition, has said that the only way for a political solution to end the Syrian war is for peace talks in Geneva to take place.

"There is no other political solution," French Foreign Minister Laurent Fabius said speaking on behalf of the group on Sunday.

"There will be no political solution for Syria unless Geneva 2 meets."

An international meeting bringing President Bashar al-Assad's government and opposition groups to the table is set to be held from January 22 in Switzerland.

The main opposition bloc, the National Coalition, is under intense pressure to confirm its participation and has said it will decide on the issue on January 17.

"We urge the National Coalition to respond positively to the invitation to set up the Syrian opposition delegation sent by the UN Secretary General," the 11-nation Friends of Syria group said in a joint statement.

"We invite them to form, as soon as possible, a delegation of opposition forces to participate in the political process."

The leader of the Coalition, Ahmad Jarba, attended the Paris talks and said in a news conference that the Friends of Syria had agreed that Assad and his family will have no role in the country's future.

"We are all in agreement to say that Assad has no future in Syria," he said.

The Friends of Syria grouping is made up of the US, Britain, France, Germany, Italy, Turkey, Saudi Arabia, the United Arab Emirates, Qatar, Egypt and Jordan.

The Syrian regime has said it will attend the conference in Switzerland but that Assad stepping down is not an option.

Army offensive

On the ground in Syria, regime troops have started moving towards rebel positions on the outskirts of Aleppo city, including the strategic district of Sheikh Najjar.

The territory is the main point of entrance into the rebel-controlled east, and by taking it, the government could effectively block supply lines from Turkey, Al Jazeera's Zeina Khodr said on Sunday.

"The rebels are bogged down in their own war in the opposition-held north and the regime is trying to push forward, trying to make advances," our correspondent reported from Beirut.

Activists said the army was also attempting to push towards a strategic highway linking the airport to the western part of city, which remains under government control.

The government's push comes amid fierce infighting between various armed opposition groups, primarily directed against al-Qaeda-linked fighters in the Islamic State of Iraq and the Levant (ISIL).

At least 700 people have been killed in the past nine days as rebel forces turned on each other, while dozens of fighters from both sides were kidnapped, the Britain-based Syrian Observatory for Human Rights said.