Kurdish-controlled areas of northern Syria are expected to declare a federal system imminently, a Kurdish official says, as peace negotiations continue to be held in Switzerland about how to end the country's five-year war.

The step, which would combine three Kurdish-led autonomous areas of northern Syria into a federal system, is sure to anger neighbouring Turkey, which fears growing Kurdish power in Syria is encouraging separatism among its own Kurdish minority.

Idris Nassan, a Syrian Kurdish official and former leader in the Syrian Kurdish Democratic Union Party (PYD), says the announcement will mean "widening the framework of self-administration" across northern Syria.

Speaking to Al Jazeera from Kobane, in Syria, on Wednesday, Nassan said preparations for federalism have been ongoing for quite some time and an announcement would be made shortly.

"Federalism should be the future not only for northern Syria or the Kurdish regions but for Syria in general, because under federalism democracy and equality will be guaranteed," he said.

Al Jazeera's Diplomatic Editor James Bays, reporting from Geneva, said the PYD has so far been left out of the peace talks, making the timing of the federalism announcement significant.

"I think the timing is very significant, making this announcement as the talks restart for the third day," he said.

"The time has been chosen by the PYD to say 'Don't forget about us', because they have been excluded from this process here in Geneva."

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The PYD was not invited to Geneva, in line with the wishes of Turkey, which sees it as an extension of the Kurdistan Workers' Party (PKK), which it is battling in southeastern Turkey.

Federalism in Syria has been discussed openly in recent weeks after Sergei Ryabkov, Russian deputy foreign minister, floated the idea in the media ahead of the start of the Geneva talks.

"If as a result of talks, consultations and discussions on Syria's future state order ... they come to an opinion that namely this [federal] model will work to serve the task of preserving Syria as a united, independent and sovereign nation, then who will object to this?" Ryabkov said in February.

Then, in an interview with Al Jazeera, Staffan de Mistura, the UN special envoy for Syria, said the idea of federalism is likely to be discussed among the parties at the Geneva talks.

President Bashar al-Assad's government, however, has consistently said no political decisions will be "imposed" on the country.

One of Assad's senior advisers was cited by state television on Wednesday as rejecting any calls for federalism.

The development out of the Kurdish-controlled areas of Syria came as Russia continued to withdraw its forces from Syria, a move that de Mistura declared as "significant" .