"Yesterday, the President authorized the Department of Defense to equip Kurdish elements of the Syrian Democratic Forces as necessary to ensure a clear victory over ISIS in Raqqa, Syria," chief Pentagon spokesperson Dana White said in a statement referring to ISIS' self-declared capital.
The equipment provided is set to include small arms, machine guns, construction equipment and armored vehicles, a US official told CNN. The supplies and weapons will be parceled out to be just enough to accomplish specific objectives related to Raqqa, the official added.
It is a move that has long been under consideration at the Pentagon but has been delayed due to strong opposition from American NATO ally Turkey.
Ankara sees the Kurdish fighters in the Syrian Democratic Forces -- known as the YPG -- as closely linked to the PKK, an internationally designated terror group that has carried out attacks against Turkey. The US views the two Kurdish groups as distinct organizations.
The US official said several administration brass, including Defense Secretary James Mattis, talked to Turkish interlocutors Tuesday to explain the US decision.
Mattis met with counterparts in Copenhagen Tuesday as part of a conference focused on the ISIS fight, also attended by the Turkish minister of defense.
"We've been conducting military and diplomatic dialogues with the Turks and it was a very, very useful discussion today," Mattis told reporters Tuesday following the meeting, while not addressing the issue of arming the Kurds directly.
Under Secretary of State Tom Shannon also had a closed meeting with Turkish presidential adviser Ibrahim Kalin Tuesday at the State Department.
The US sees the 50,000-strong Syrian Democratic Forces as the most effective force fighting ISIS in Syria and has armed the non-Kurdish Arab elements of that group for some time. Syrian Kurds make up just over half of the SDF, according to the US military.
The Pentagon said that it would continue prioritizing the arming of Arab forces in Syria, but acknowledged Ankara's concerns in the statement announcing the decision.
"We are keenly aware of the security concerns of our coalition partner Turkey. We want to reassure the people and government of Turkey that the US is committed to preventing additional security risks and protecting our NATO ally," White said.
But she called the Syrian Democratic Forces "the only force on the ground that can successfully seize Raqqa in the near future," an indirect pushback on Turkish proposals that the US abandon its support of the YPG and instead rely on other Turkish-backed rebels for the crucial mission.
This is not the first time Washington and Ankara have differed publicly on their views of the Syrian Kurds.
Turkey carried out a series of airstrikes against the YPG last month, a move that drew immediate complaints from US officials.