The top aide to Iran’s Supreme Leader has threatened attacks on the Kurdish-led, US-backed force that holds much of northern and eastern Syria.

Ali Akbar Velayati (pictured) said an offensive by the Assad regime would soon take Raqqa city in northern Syria, captured by the SDF in October from the Islamic State, and SDF-held territory east of the Euphrates River.

A pro-Assad force — including Iranian troops, Hezbollah, and Iranian-supported foreign militias — has regained parts of eastern Syria from ISIS, including the takeover of Deir ez-Zor city on Friday. Meanwhile, the SDF has added to its gains with parts of Deir ez-Zor Province, including major oilfields.

The outcome has added to the de facto partition of Syria, with a Kurdish autonomous region across much of the north and east. Bashar al-Assad and his top advisors have ruled out a federal system with the Kurdish region, with one advisor, Bouthaina Shaaban, saying there soon will be a battle between the regime and the Kurds for the areas seized from ISIS.

“Liberation” of Raqqa?

Last week the regime proclaimed that Raqqa was an “occupied” city which it would eventually “liberate”.

The future system of rule of Raqqa, which had been controlled by ISIS since late 2013, is unclear. For now, the SDF is backing a local council for the city, which has a mainly-Arab population.

Velayati’s statement is the strongest yet by Iran that it will back Assad in an offensive against the Kurds:

We will witness in the near future the advance of government and popular forces in Syria and east of the Euphrates, and the liberation of Raqqa city.

The aide also denounced the US for its backing of the SDF, accusing Washington of seeking to divide Syria.

Russia, whose airstrikes and ground support are essential for the pro-Assad forces, has made no response so far to the Iranian statement.

While propping up the Assad regime, especially since 2015, Moscow and Tehran have been in an uneasy alliance in recent months about the future of Syria. While Iran has publicly endorsed the Assad regime’s reclaiming of territory, Russia has pursued “de-escalation zones” — nominally endorsed by Iran — which would bolster the short-term partition, with opposition-held Idlib Province in the northwest and opposition areas in the south as well as the Kurdish region in the north and east.