The United States is opposed to any unilateral declarations of autonomous federal zones in Syria but would not be against federalism if the Syrian people chose it as part of a negotiated political settlement.
State Department spokesman Mark Toner spelled out Washington's position after the main Syrian Kurdish party said it would soon declare a federal region in the country's north.
The party said the region's Kurds, Arabs and Turkmen would all be represented, calling it a model for the rest of the country.
Both Turkey and the Syrian government are opposed to such a declaration, fearing that it could lead to the country's partition.