What’s more important: your relationship with Turkey—your NATO ally—or the potential to make significant inroads against Daesh in Syria? That’s the question Ankara is asking the Obama administration following a spate of deadly terrorist attacks ^[1] in Turkey in recent months that have further inflamed tensions between the Turkish government and the Turkish Kurds. Despite attempts by the US ^[2] to calm the waters, the answer may be one Turkish President Erdogan isn’t going to like—while Turkey remains an important strategic partner for the US, the US’s cooperation with Kurdish forces in Syria is indispensable.

Turkey’s interpretation of this dilemma is relatively black and white. For Turkey, the Democratic Union Party (PYD)—the Kurd’s main political force in Syria—and its armed wing, the People’s Protection Unit (YPG), are terrorist organisations directly linked to Turkey’s Kurdistan Workers’ Party ^[3] (PKK)—which Turkey, the UK, US, EU and Australia all consider a terrorist group ^[4]. Erdogan’s government has made the destruction of the PKK a priority ^[5] since hostilities between the two sides resumed following the collapse of a two-year ceasefire ^[6] in June last year.

Added to that tension, Ankara fears ^[7] Syrian Kurds are manipulating the violence in Syria to carve out territory for an autonomous region—as Iraqi Kurds succeeded in doing in northern Iraq ^[8]—along the border with Turkey, and have warned the YPG ^[9] not to cross west of the Euphrates. Those fears aren’t unfounded, with the PYD announcing the formation ^[10] of the Federal Democratic System of Rojava and Northern Syria on 17 March, a move that the US, the Syrian and Turkish governments—as well as rival Kurdish groups—have unanimously condemned ^[11]. In a nutshell, from a Turkish perspective, any assistance to Kurdish forces on either side of the border equates to the support of terrorism against Turkey.

The US has taken a decidedly different approach to the issue of Kurdish forces. While acknowledging the PKK as a terrorist organisation and calling upon the PKK to cease attacks against Turkish citizens ^[12], the Obama administration has been at pains ^[13] to distinguish the PYD from its Kurdish compatriots in Turkey. The Turkish government has been infuriated by this response, with Erdogan using a recent visit to Washington ^[14] to call for the US to change its position on the PYD.

In an attempt to calm hostilities and direct attention back to Syria, Washington has urged all parties to focus on the common threat of Daesh ^[15], calling on Turkey to cease its cross-border artillery fire into Syria and warning the YPG not to ‘take advantage of a confusing situation’ and seize new territory on the Turkish border.

Regardless of Turkey’s displeasure, the US has little choice but to persist with its support for the PYD. The Obama administration has made it clear ^[16] that its primary goal in Syria is the destruction of Daesh and time is running out to make significant progress before Obama leaves office. While the US currently has 50 special operations forces ^[17] advising and assisting local fighters in Syria, it appears unlikely they’ll seek to increase their ground involvement in the near future. The US, therefore, must rely on Kurdish forces on the ground to drive back Daesh.

Successful campaigns ^[18] over the past four years have proven that Syrian Kurdish forces, like their counterparts in Iraq, are a reliable and organised strategic partner for the US. They’ve filled the void left by Syrian government forces when they moved towards Aleppo ^[19] in 2012, and have effectively established self-rule ^[20] in three regions collectively known as Rojava in the country’s northeast. With the assistance of US-led airstrikes ^[21], they’re squeezing IS around its bastion in Raqqa and across the border in north-western Iraq, and are expected ^[22] to move towards the Aleppo region, where the US is yet to play a significant role in countering Daesh.

While the PYD may not be the ideal US ally, there are no valid alternatives capable of achieving the US’ desired results. The US can’t support Syrian President Bashar al-Assad’s brutal and historically anti-Western regime, despite the dictator solidifying his leadership position in recent months ^[23]. Other potential partners for the US are equally distasteful, such as Hezbollah, the al-Qaeda-linked Nusra Front (considered a direct terrorist threat to the US) and a handful of relatively moderate, but largely disorganised, Sunni groups.

Intertwined with this is the Russia factor. Moscow appears more than willing to take advantage of any US hesitancy to fully support the Kurds because of fears it’ll further strain the US–Turkey relationship. Putin knows that Kurds aren’t pawns in the Syrian conflict, and will consider siding with whoever offers them the greatest security. Putin’s already stepped up Russia’s support for the Kurds ^[24] in recent months. In perhaps a sign of things to come, the PYD opened its first foreign office in Moscow ^[25] in February, with a ceremony attended by Russian foreign ministry officials.

To counteract this, the US needs to take Turkey out of considerations in Syria, and as it successfully managed to do so in northern Iraq ^[26], convince the Kurds to choose the West over Russia. While Ankara may continue to voice its displeasure and carry out attacks against the YPG ^[27] in Syria, it won’t change Obama’s mind.

Turkey will need to accept that the US’s end-game—unlike their own ^[28]—mightn’t necessarily feature the removal of Assad from power. Instead, Washington wants to eliminate the threat of Daesh, and they’re going to need the Kurds to do it.