Kurdish parties say they are planning to declare a new federal system in areas they control in northern Syria.
The Kurds already operate "autonomous administrations" in three enclaves bordering Turkey - Afrin and Kobane in Aleppo province and Jazira in Hassakeh.
The federal system would also include predominantly Arab and Turkmen areas captured from so-called Islamic State.
The idea was dismissed by Syrian government negotiators at peace talks in Geneva and by Turkey's government.
Both stressed the need to preserve Syria's national unity and territorial integrity.
Kurds made up between 7% and 10% of Syria's population of 24.5 million before the uprising against President Bashar al-Assad began five years ago.
Although they were denied basic rights and suffered decades of political suppression by the Arab-led state, most Kurds avoided taking sides when a wave of protests swept the country.
When government forces withdrew from Kurdish areas to concentrate on fighting predominantly Arab rebels elsewhere in mid-2012, Kurdish militias swiftly took control, led by the Popular Protection Units (YPG) of the Democratic Union Party (PYD).
In January 2014, the PYD and other Kurdish parties created autonomous administrations based in the enclaves, or "cantons", of Afrin, Kobane and Jazira.
They stressed at the time that they were not seeking independence from Syria, but "local democratic administration" within a federal framework.
In September 2014, the jihadist group Islamic State (IS) launched an assault on Kobane, prompting tens of thousands of people to flee to Turkey. With the help of US air power, the YPG regained control of the town after a four-month battle.
Since then, the YPG has inflicted a series of defeats on IS and established control over 26,000 sq km (10,000 sq miles) of Syria, according to one estimate, including a 400km (250-mile) stretch of territory along the Turkish border.
The plan to create a federal system to administer the three cantons and the territory captured from IS was circulated ahead of a meeting of about 200 Kurdish representatives in the town of Rmeilan on Wednesday.
Kurdish official Idris Nassan told the Reuters news agency that a federal arrangement would widen "the framework of self-administration that the Kurds and others have formed" and would represent all ethnic groups.
An official declaration was expected on Wednesday but was postponed for "logistical reasons" and because of concerns expressed by local Arab and Assyrian communities, according to the UK-based Syrian Observatory for Human Rights.
When asked about the Kurdish plan, the Syrian government's chief negotiator at the peace talks in Geneva said he would not comment on "unilateral statements coming from here and there".
But he warned: "Betting on creating any kind of divisions among the Syrians will be a total failure."
Turkey, which backs Syria's opposition and sees the PYD as an extension of the rebel Turkish Kurdistan Workers' Party (PKK), also rejected the idea.
"Syria's national unity and territorial integrity is fundamental for us. Outside of this, unilateral decisions cannot have validity," a foreign ministry official told Reuters.