Trump is expected to officially inform Erdogan of his decision Tuesday, when he visits the White House.
President Donald Trump has authorized arming Kurdish fighters in Syria "as necessary to ensure a clear victory" in a planned assault to retake the city of Raqqa from Islamic State, the Pentagon said on Tuesday, in a likely blow to U.S. ties with Turkey.
"The SDF, partnered with enabling support from US and coalition forces, are the only force on the ground that can successfully seize Raqqa in the near future", said White.
Turkey has continued to lobby the Trump administration to change course in the days leading up to President Recep Tayyip Erdogan's United States visit, dispatching top Turkish officials, including General Hulusi Akar, the military chief of staff, and Hakan Fidan, the intelligence chief, to Washington.
"The U.S. continues to prioritize our support for Arab elements of the SDF", said White.
The YPG forms the backbone of the SDF's forces.
The decision is meant to accelerate the Raqqa operation, but it clashes with the Turkish government's view that the Syrian Kurdish group known as the YPG is an extension of Kurdish terrorist organization that operates in Turkey.
The YPG includes the Syrian Democratic Forces of Arab, Christian and Turkmen fighters.
The jihadists' capital of their supposed "caliphate" is being surrounded by a Kurdish and Syrian Arab alliance and officials are expecting a brutal fight to retake the city.More news: Red Sox ban fan from Fenway for racist taunt
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Defense Secretary Jim Mattis said Tuesday he had useful discussions with Turkey and the two countries are working out differences over a US alliance with Syrian Kurds in fighting Islamic State militants.
"We were troubled by that", Air Force Col. John Dorrian, a spokesman for Combined Joint Task Force-Operation Inherent Resolve, said of Turkey's failure to give adequate warning of airstrikes in the Hasaka area.
"We had forces within six miles of the strikes", Dorrian said.
The announcement comes after Secretary of State Rex Tillerson met with Turkish officials last week in Ankara, Turkey, and discussed possible strategies for defeating ISIS in Syria.
But a group of Kurdish fighters, commonly referred to as the People's Protection Units or YPG, is considered a terrorist organization by Turkey, another USA ally fighting ISIS.
The United States has played down Turkish accusations of links between the YPG and PKK.
There are now more than 1,000 American service members in Syria, after the Pentagon sent about 400 additional Marines to Syria in March to prepare for the Raqqa offensive. "We're going to sort it out, we'll figure out how to do it, but we're all committed to it".
Turkey carried out a series of airstrikes against the YPG last month, a move that drew immediate complaints from U.S. officials.
The sources said the Turks would be notified about the decision soon.