Mattis "reiterated US commitment to protecting our North Atlantic Treaty Organisation ally", spokeswoman Dana White said in a statement. Turkey contends the SDF's Syrian Kurdish militia, known as the YPG, is a terrorist group affiliated with the outlawed PKK, the Kurdistan Workers' Party, a terror group that has been battling the Turkish state for many years.
"The Trump administration providing arms to a terrorist organization - either directly or indirectly through the YPG - does not change the fact that this amounts to support to a terror organization". Canikli told Turkey's A Haber television.
It was not immediately clear whether the decision by Trump means the YPG will receive heavier weapons, including anti-tank missiles and armored vehicles.
Turkish President Recep Tayyip Erdogan said on Wednesday that he hoped the decision will be changed by the time he visits Washington for talks with Trump next week.
The battle for the recapture of Tabqah began almost two months ago when American helicopters inserted hundreds of Syrian fighters into the city, along with a handful of American special operations forces.
The SOHR report stated the ISIS militants were to withdraw from the SDF-held areas into the ISIS-controlled ones, including to Raqqa, the group's de facto capital in Syria. Daesh is the Arabic acronym for IS.
US-backed Syrian Democratic Forces (SDF) on Wednesday (10 May) captured Syria's Tabqa town from the Isis as part of their campaign to liberate Raqqa from the Islamist jihadists.
"This is yet another victory by the SAC and the SDF, our most committed and capable ground force partners in the fight against ISIS", coalition spokesman U.S. Col. John Dorrian said in a Central Command statement released Thursday. "A negative outcome will also emerge for the United States".
The Arab-Kurdish alliance accepted ISIL's surrender to protect civilians and the dam, it said, adding "the coalition tracked fleeing fighters and targeted those that could be safely hit".
Turkey's deputy prime minister says the USA decision to supply weapons to Kurdish fighters battling Islamic State militants in Syria is "unacceptable".
Ms White also stressed the Pentagon was "keenly aware" of Turkey's concerns.
"We expect that this mistake is to be rectified", he said, days ahead of a crunch meeting in Washington between Turkish President Recep Tayyip Erdogan and USA counterpart Donald Trump.
The Turkish leader vowed to table the issue during next week visit to Washington.
In an effort to retake ISIS' last major stronghold, President Trump has approved arming Kurdish forces in Syria despite opposition from Turkey.
The news about the United States plan to arm Syrian Kurds comes, as the Trump administration mulls sending as many as 5,000 more troops to Afghanistan, a military official told NBC News, and as the White House makes moves it believe will help American forces "start winning" again in the region.
"The argument that a ground operation in the fight against Daesh would be successful only with YPG has nothing to do with reality", he said.