Turkish President Recep Tayyip Erdogan gestures as he speaks in April during the Atlantic Council summit in Istanbul. (Ozan Kose/Agence France-Presse via Getty Images)

President Trump seduced the Chinese president with a “beautiful piece of chocolate cake,” along with the news of missile strikes in Syria. But he will need more than nice pastries to win over Turkey’s strongman when President Recep Tayyip Erdogan visits the White House next week.

If reports are true, Trump will tell his Turkish counterpart that the United States has decided to arm Syrian Kurdish forces in the upcoming offensive to take the Islamic State stronghold of Raqqa. Erdogan considers the Syrian Kurdish forces “terrorists” with strong links to the Kurdistan Workers’ Party (PKK) currently waging war against government forces in southeastern Turkey.

The primary goal of Erdogan’s Syria policy has become preventing the rise of a Kurdish entity in northern Syria at all costs — including through harsh policies toward Turkey’s own Kurds, who are cheering the rise of their brethren across the border. Erdogan can’t lash out at Trump, as he does at his domestic opponents, but he will not be happy that Trump is frustrating his goal.

And no matter how good the cake is, there is trouble ahead in relations with this close NATO ally. The United States can expect Turkey to demonstrate its displeasure by targeting U.S.-supported Kurdish forces in Syria. Ankara will also be more reluctant to work with Washington in fighting the Islamic State or rolling back Iranian influence in the region, a priority for the Trump administration.

What to do? The answer lies in an interview candidate Trump gave in July 2016. Asked how he would handle Turkish-Kurdish enmity in Syria by the New York Times, Trump said, “Well, it would be ideal if we could get them all together. … I’m a big fan of the Kurdish forces. At the same time, I think we have a potentially — we could have a potentially very successful relationship with Turkey. And it would be really wonderful if we could put them somehow both together.”

His plan lacks eloquence, but it is basically the right idea. One of the shortcomings of the Obama administration’s policy was the assumption that the Kurdish issue in Syria could be dealt separately from the PKK insurgency in Turkey. But Turkey’s Kurds and Syria’s Kurdish forces are deeply intertwined – culturally, politically and militarily.

The United States told itself that arming the Syrian Kurdish forces would have no impact on the situation in Turkey. But as Washington has turned a blind eye, the Kurdish situation within Turkey has deteriorated dramatically. In the summer of 2015, the Turkey and the PKK broke off peace talks and resumed fighting, in part because of their rivalry in Syria. Since then, the PKK has been targeting Turkish security forces and cities. In retaliation, the Turkish government has been pursuing a scorched-earth campaign in Kurdish areas and crushing Kurds politically.

All of Turkey is paying a price. The general decline in its democratic standards is in part due to the Kurdish conflict. The resumption of violence has accelerated Erdogan’s authoritarian drift away from democracy. The leader of Turkey’s pro-Kurdish HDP party, Selahattin Demirtas, is in jail, along with 85 majors and 14 Kurdish deputies elected to serve in the Turkish parliament. Turkey has more journalists in jail than any other country on earth — many on allegations that they are indirectly supporting terrorism through their articles or columns.

Trump should no longer ignore the larger Kurdish issue. Washington should instead develop a more comprehensive policy and push for a Turkish-Kurdish peace deal on all fronts. Trump can use his meeting with Erdogan to discuss a number of carefully coordinated steps that might persuade the Turkish leader to get back to the peace negotiations with Kurds.

The first order of business would be to broker a PKK cease-fire inside Turkey, which the United States can arrange through its Syrian Kurdish contacts. Once the PKK declares a cease-fire inside Turkey, Erdogan would have little excuse to continue his hard-line position on the Kurdish issue. The Turkish-Kurdish thaw could initially start in Syria, between Turkish forces and Syrian Kurds or through their political representatives in Europe, and later spread to Turkey.

For such a deal to work, the Turkish president would want assurances that the Syrian Kurds would not overreach, go for statehood or try to govern non-Kurdish Sunni areas of Syria. Fine. Similarly, Kurds would seek guarantees that they can keep autonomous Kurdish zones inside Syria and that Turkey would not try to reverse their territorial gains.

Both conditions are achievable if the United States will guarantee limited autonomy for Kurdish-populated towns and allow Turkey to become the patron for the remaining Sunni Arab (non-Kurdish) cities of northern Syria — which should be similarly self-governing. It requires a U.S. commitment beyond the anti-Islamic State military campaign but could well serve as the basis of a transition to a new governance model in Syria.

The alternative — arming the Syrian Kurds but ignoring Turkey as it becomes even more engulfed in its domestic turmoil — will only contribute to regional chaos. It would ultimately derail U.S. plans against the Islamic State and Iran. It would weaken a NATO ally and the burgeoning Kurdish entity in Syria — one of the few islands of stability in that war-torn country. The only sustainable long-term scenario for the north of Syria involves a Turkish-Kurdish fortress against jihadists and a real peace deal.

As Trump says, “It would be really wonderful if we could put them somehow both together.” He’s right. And, at that meeting, if it happens, it would make sense to serve cake.