PARIS: The main Western-backed Syrian opposition has gained little by demanding the fall of President Bashar al-Assad other than fuelling killings and the refugee crisis, a senior official from Syrian's northern Kurdish region said on Monday.

Syrian Kurds and their allies are finalising plans for an autonomous political federation in the northern part of the country. They are pressing ahead despite the objections of foreign governments which fear Syria's disintegration and alarm from neighbouring Turkey, which fears a growing Kurdish sway in Syria is fuelling separatism among its own minority Kurds.

While talks to end the five-year conflict in Syria struggle, the plans are taking shape independently of United Nations-led diplomacy and creating facts on the ground in an area of the country known in Kurdish as Rojava.

"The problem is not the fall of Assad or people that are ruling, but changing (the) system," Sinam Mohamed, a member of the Syrian Kurdish Democratic Union (PYD) told reporters in Paris.

"It's not matter of fighting Assad or not. It's how do you change the system from a dictatorship into a democratic system in Syria. Look at the other opposition, they called for the fall of Assad, but they have gained nothing but killing and many refugees," she said.

The PYD has been left out of the faltering Geneva peace process, where the main Western, Arab and Turkish-backed High Negotiations Committee (HNC) opposition group has suspended its participation after it accused the government of breaking a fragile truce and blocking aid to besieged areas.

The HNC, which does include Kurdish groups, has accused the PYD and its allies of tacitly supporting Assad.

Sinam Mohamed is co-chair of the alliance led by the PYD. It controls an uninterrupted stretch of 400 km (250 miles) along the Syrian-Turkish border from the Euphrates River to the frontier with Iraq, where Iraqi Kurds have enjoyed autonomy since the early 1990s. They also hold a separate section of the northwestern border in the Afrin area.

She was speaking after opening a fourth overseas representative office for Rojava following similar moves in Moscow, Berlin and Stockholm. She said they aimed at giving the Syrian Kurds a voice overseas and promoting them as the best military force to defeat Islamic State militants in Syria.

"Our priority is to defeat terrorism and build stability in Syria," Mohamed said.

The French foreign ministry said it did not recognise the legitimacy of the Kurdish representative office. However, France is part of the US-led coalition that is carrying out air strikes in support of the PYD's military wing, the YPG, and groups fighting with it as they make advances towards Islamic State's bastion of Raqqa.