ISTANBUL — The end of the ceasefire between Turkey and the PKK (The Kurdistan Worker's Party) is a development that will undermine both sides' bigger plans in the region.

The Turkish government may be hoping to gain the nationalist vote and weaken the legal pro-Kurdish party (The People's Democratic Party or HDP) by going after the PKK, but it will go a long way in damaging key foreign policy objectives in Syria and Iraq. Likewise for the PKK, a new clash with Turkey could mean losing the credibility the insurgent group had won in both the region and the international arena since 2014.

Turkey has been bombing PKK targets in northern Iraq for days. Weakening the PKK and its Syrian arm, the PYD, is bound to strengthen the Islamist ISIS troops across the region. The most effective resistance against ISIS has been carried out by Kurdish troops under the command of the PKK. The Kurds acted like the de facto land force of the anti-ISIS coalition led by the U.S.

Aiming at the PKK and the PYD will also be a boost for Bashar al-Assad's regime, which the Turkish government has been trying to topple for years. How is that related? Let us go back to the beginning.

The Syrian Kurds of the PYD have been accused of neither targeting the Damascus regime nor even allying with it. But one of the important reasons the PYD did not join the anti-Assad opposition is Turkey. Ankara exercised its influence on the Syrian opposition to keep out the PYD, working instead with the Kurdish National Council, founded by the support of Iraqi Kurd leader Masoud Barzani.

Robert Ford was the U.S. ambassador to Syria back in 2012 and is one of the experts at the Middle East Institute where I also work. "The PYD said they want to join the Syrian opposition ranks at the Syrian meeting we organized in Europe in 2012," Ford recalled recently. "We did not allow the PYD to join due to pressure from Ankara. Now, we face a completely new Kurdish reality."

The state of the war might be different if the PYD had been allowed to join at the beginning. Now, Ankara is insisting on making the same mistake again, pushing the Kurds towards the regime and Iran by trying to isolate the PYD.

Kurdish news sources have reported about a meeting that took place in Suleymaniyah last June between the PYD's military wing, Jalal Talabani's Patriotic Union of Kurdistan and Iran's Revolutionary Guard. According to the reports, Iran promised the PYD that they would receive whatever support the regime gets plus autonomy if they accept to fight on the side of the regime.

President Hassan Rouhani recently declared: "Iran protects Erbil and Baghdad the same as it protects Iranian Kurdistan … Without Iran's help, Erbil and Baghdad would be in the hands of terrorist groups right now. The way we protect Sanandaj, we also protect Sulaimani and Duhok."

This is a dangerous development. The PYD joining the regime is bound to only prolong the war in Syria, and strengthen radicals like ISIS. Turkey is uneasy about American cooperation with the PYD against ISIS, even if the PYD turned out to be a constructive actor in Syria, managing to move closer to the West and allowing cooperation with the Free Syrian Army that Turkey supports.

But there is short-sightedness on both sides. If the PKK/PYD deepens its clash with Turkey, it risks undoing all the good will it received from its struggle against ISIS after the radical group captured Mosul. Western media was busy publishing picture after picture of the female militants in the PYD, describing the group as a progressive Kurdish movement that is secular and respectful of the rights of minorities and women. There were discussions in the European Parliament and the U.S. Congress about removing the PKK from terrorism lists.

The PKK is endangering all this progress by fighting Turkey once again. Not only do the Kurdish forces destroy its credibility gained in the fight against ISIS, but it serves the interests of both Tehran and Damascus.