Erdogan also called on the United States to stand alongside a North Atlantic Treaty Organisation ally - Turkey - and reverse its decision on arming Syrian Kurds before his upcoming visit to Washington.
Turkish Foreign Minister Mevlut Cavusoglu, speaking during a visit to Montenegro yesterday, said weapons supplied to the YPG had, in the past, fallen into PKK hands. The issue risks further stoking tensions between Ankara and Washington less than a week before President Recep Tayyip Erdogan heads to Washington to meet his U.S. counterpart Donald Trump in their first face-to-face encounter as heads of state. "The supply of arms to the YPG is unacceptable", deputy PM Nurettin Canikli told A Haber television.
Ankara views the YPG as the Syrian extension of the PKK militant group, which is labeled a terrorist organization by both Ankara and Washington.
Turkey slammed the United States decision to arm the Kurdish People s Protection Units (YPG), which Ankara considers terrorists but which Washington sees as an indispensable ally in the fight against IS.
The issue risks further stoking tensions between Ankara and Washington less than a week before President Recep Tayyip Erdogan heads to Washington to meet his USA counterpart Donald Trump, in their first face-to-face encounter as heads of state.
Pentagon spokeswoman Dana White said Trump has authorized equipping "Kurdish elements of the Syrian Democratic Forces (SDF) as necessary to ensure a clear victory over ISIS" in Raqqa.
The Kurdish Workers' Party has fought Turkey for Kurdish autonomy in the country for 30 years, the BBC News noted.
Spokesman Redur Xelil said the move was "somewhat late", but would still "provide a strong impetus" to forces fighting IS.More news: André Holland to star in Stephen King Hulu series Castle Rock
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"The decision was a mistake and the United States should reverse it".
Turkey, which has sent troops to northern Syrian in an effort to curtail Kurdish expansion along its borders, has for months tried to lobby Washington to cut off ties with the Kurds and work instead with Turkish-backed opposition fighters in the fight for Raqqa. Erdogan accused the Trump administration on Wednesday of siding with terrorists.
Erdogan vowed to bring up "our worries" on the issue in talks with US President Donald Trump on May 16 in Washington.
Washington has relied heavily on the YPG in its campaign against Daesh but until recently had not directly armed the group as a matter of policy.
Mr Sinan Ulgen, a former Turkish diplomat and analyst at Carnegie Europe, said: "Turkey doesn't have much room to move here".
In response, the US -led coalition has focused its air and artillery strikes on eliminating those defenses and the construction equipment that ISIS uses to build them, Dorrian said.
"The SDF's success against ISIS demonstrates the power of working by, with and through local partner forces fighting ISIS, among their own people, in their own territory", Dorrian said in the statement.