Turkish President Recep Tayyip Erdogan says he will grill President Donald Trump about the U.S. decision to arm the Syrian Kurdish militia when he visits Washington next week.
"The fight against the terrorist organization Daesh [the Arabic acronym for Islamic State] should not be carried out with another terrorist organization," Erdogan said Wednesday. "This kind of step would endanger the future of Syria and the region."
The YPG Kurdish militia is widely recognized as the most effective in Syria in fighting Islamic State.
However, it is considered by Ankara to be an affiliate of the Kurdistan Workers' party, PKK, which is fighting the Turkish state. Turkey and the U.S. have designated the PKK as a terrorist organization.
"Every weapon obtained by the People's Protection Units [YPG] constitutes a threat to Turkey," declared Foreign Minister Mevlut Cavusoglu.
Erdogan in Washington
Erdogan's Washington visit is seen as the most important leg of his international tour to bolster his legitimacy, after last month's controversial referendum victory granting him sweeping powers. The vote remains marred by voter fraud allegations.
The ongoing controversy over Kurdish fighters is a point of contention between allies, especially as most experts predicted Washington would ultimately arm the YPG.
"It's obvious Americans are quite pragmatic about the Syrian question," said Atilla Yesilada, political consultant of Global Source Partners. "They prefer Kurds, not because they are in love with them, but simply because Kurds have 50,000 valiant fighters at the gates of Raqqa. What they need is heavy weaponry."
Weapons and PKK
The kind of weapons Washington will ultimately deliver to the YPG will likely be closely followed by Ankara. The Turkish military has repeatedly claimed that sophisticated anti-tank missiles delivered by its Western allies to Syrian Kurdish forces have fallen into the hands of the PKK fighting in Turkey.
Washington is going on the charm offensive.
"We'll work out any of the concerns," U.S. Defense Secretary Jim Mattis said Wednesday. "We will work very closely with Turkey in support of their security on their southern border. It's Europe's southern border, and we'll stay closely connected."
But the YPG is still claiming victory.
"We believe that from now on and after this historic decision, [the YPG] will play a stronger, more influential and more decisive role in combating terrorism at a fast pace," spokesman Redur Xelil said in a written statement to Reuters.
Ankara has threatened retaliation against its Western partners if they pursued a policy of arming what it considers to be terrorists. U.S. forces depend heavily on the Incirlik air base in southern Turkey, not only for military operations against Islamic State, but also as a strategic logistics hub. Turkish ministers from time to time have threatened Washington over its use, but analysts predict Ankara remains reluctant to take such a drastic step and risk wrecking relations with Trump.
Erdogan has met with his Russian counterpart, Vladimir Putin, five times in less than a year, most recently this month in Sochi. But given that Moscow also is backing the YPG, Ankara's room for maneuvering is viewed as limited.
Washington's decision to support the YPG will also likely preclude any repeat of last month's Turkish military strikes against the Syrian Kurdish militia, both in Syria and Iraq.
"The Americans have pushed Ankara into a corner where no military operations against the presence of YPG in Syria are possible and, second, Ankara from now on will have to live with the fact the YPG is a political organization like any other that is fighting Islamic State," said former senior Turkish diplomat Aydin Selcen.
VOA's Kenneth Schwartz contributed to this report.