Chris Van Hollen, a Democrat, and fellow US Senator Lindsey Graham, a Republican, have threatened to push for sanctions against Turkish President Recep Tayyip Erdogan unless he forces Ankara-backed Syrian militia into a ceasefire with US-allied Kurdish fighters in northeastern Syria.

The Hill reported their standpoint on the afternoon of December 17 in Washington DC, hours before Reuters reported the US State Department as saying a ceasefire between Turkish forces and US-backed and Kurdish-led Syrian Democratic Forces (SDF) present in the vicinity of the northern Syrian city of Manbij had been extended until the end of this week.

Van Hollen and Graham said that they were prepared to introduce sanctions legislation this week against Turkey if Ankara did not immediately agree terms for a sustained ceasefire and demilitarised zone. 

“While Turkey has some legitimate security concerns that can be addressed, these developments are undermining regional security, and the United States cannot sit idly by,” the senators wrote. 

“In the wake of the Assad regime’s fall, Turkish-backed forces have ramped up attacks against our Syrian Kurdish partners, once again threatening the vital mission of preventing the resurgence of ISIS [Islamic State].”

Washington brokered an initial ceasefire last week following fighting that broke out around the same time that Turkish-backed opposition groups advanced on Damascus and overthrew the Bashar al-Assad regime that ruled for 24 years.

"We continue to engage"

“We continue to engage with the SDF, with Turkey about a path forward,” US State Department spokesperson Matthew Miller said at a regular press briefing on December 17, also stating that the US would like the ceasefire to be extended for as long as possible.

“We don’t want to see any party take advantage of the current unstable situation [in the wake of the fall of the Assad regime] to advance their own narrow interests at the expense of the broader Syrian national interest,” he added.

The SDF serves as the main partner fighting force to the US in a coalition formed against Islamic State in Syria. It is militarily led by the YPG militia, which was instrumental in destroying the Islamic State caliphate that emerged in Syria and Iraq. Ankara designates the YPG as “terrorist”, saying that it is an extension of the outlawed insurgent Kurdistan Workers’ Party (PKK) militant group that has fought the Turkish state for 40 years.

Washington is watching particularly closely for any move that Turkey or Turkish-backed forces might make on the Kurdish-controlled city of Kobani.

SDF commander Mazloum Abdi on December 17 said his group stood ready to present a proposal for a demilitarised zone in Kobani with the redeployment of security forces under US supervision and presence.

The US still has around 900 troops in northeast Syria. They support the SDF in combatting any sign of Islamic State once more significantly building up its presence and operations in Syria.

SNA "integrated Islamic State fighters"

One of the groups that mounted the offensive that caused Assad to flee to Moscow is the Syrian National Army (SNA), widely seen as an entity created by Ankara. On December 16, the self-declared Kurdish-controlled Autonomous Administration of North and East Syria, also known as Rojava, released a document identifying 415 Islamic State fighters it claimed have been integrated into SNA, raising concerns for regional security and international counter-terrorism efforts.

On December 13, RFE/RL reported that social media videos it verified showed that Central Asians and Europeans, including nationals from Albania and Bosnia-Herzegovina, feature in the ranks of Hayat Tahrir al-Sham (HTS)—the jihadist militia that grew in northern Syria under the patronage of Turkey and is now trying to form a post-Assad administration in Damascus.

At the time of the offensive, bne IntelliNews pointed out that while mainstream international media typically describe HTS as “Syrian rebels”, the group is actually to a very large extent made up of foreign mercenaries, brought to Syria to overthrow Assad.
The presence, and victories, of battle-hardened and radicalised foreign fighters will be a concern to the US and other countries in the West who fear a Syrian power vacuum could offer a base for resurgent international terrorist groups.

"This will be one of the biggest concerns from a US perspective because they aren't indigenous Syrians," Aaron Zelin, a senior fellow at the Washington Institute, told RFE/RL, adding: "The US is likely less concerned with the Syrians within HTS."

HTS is a US- and EU-designated terrorist organisation. Even Turkey designates HTS terrorist, but it is quite clear that the group could not have grown, flourished and operated in Syria just over the Turkish border without the consent of Ankara.