Trump 'backs Kurds for Raqqa assault', despite Turkish anger

US President Donald Trump will reportedly give the green light for US-backed Kurdish forces in Syria to oust the Islamic State group from Raqqa city, despite Turkish objections.

Trump will tell President Tayyip Erdogan that SDF fighters will go head with the operation to retake the extremists' Syria stronghold at a meeting in Washington later this month, US defence officials told Foreign Policy this week.

The sources, who spoke on the condition of anonymity, said that the US military was waiting for Defence Secretary Jim Mattis to approve arming the alliance of Kurdish and Arab fighters.

They added that after the approval, Trump will give his consent to the mission in spite of strong objections from Turkish authorities.

Ankara has deemed the SDF's allies the YPG a terror organisation and the Syrian branch of the PKK, which has waged an insurgency since 1984 for Kurdish independence from Turkey in a conflict that has left tens of thousands dead.

The US, however, has backed the formation of the SDF, dominated by the YPG.

Last week, a top adviser for Erdogan warned that US troops deployed along the Syrian border with Kurdish forces could be attacked, before taking back his bold comment.

The SDF this week revealed that it plans to ultimately to seize the northern part of Syria, linking the Kurdish region of Rojava with the Mediterranean Sea - another move that will infuriate Turkey.

"Arriving at the Mediterranean Sea is in our project for northern Syria, it’s a legal right for us to reach the Mediterranean," Rojava official Hediya Yousef told The Guardian.

Yousef also revealed that SDF could push west and capture Idlib the last remaining stronghold of Syria's rebel groups.

The SDF has already seized most of Raqqa province as part of its "Wrath of the Euphrates" campaign, named after the major river that cuts across the northern part of Syria.

The SDF launched its fight for Raqqa in November, just a month after US-backed forces in neighbouring Iraq announced an offensive for IS' other main stronghold, Mosul.