Washington said Tuesday it would provide weapons and equipment to the Kurdish People's Protection Units (YPG).
Washington said Tuesday it would provide weapons and equipment to the Kurdish People's Protection Units (YPG), which is a key force in the fight against IS in Syria.
"From now on, after this historic arming decision, our units will play a more influential, powerful, and decisive role in fighting terrorism at a faster pace," YPG spokeman Redur Xelil said in a statement.
He said the move had come "somewhat late," but would still "provide a strong impetus" to all forces fighting IS.
The YPG makes up the bulk of the Syrian Democratic Forces, an alliance of Arab and Kurdish fighters advancing on the northern city of Raqa, the last main stronghold for IS in Syria.
The SDF receives air support and training from the US-led coalition and is backed by special advisors on the ground.
Until Tuesday, official US policy was to supply weapons only to the Arab components of the SDF.
"The US decision to arm the YPG... is important and will hasten the defeat of terrorism," SDF spokesman Talal Sello told AFP.
Sello said the US announcement "is the result of the effectiveness of the YPG and SDF in the fight against terrorism".
The US decision has however angered Turkey, which views the YPG as a "terrorist" group because of its ties to the outlawed Kurdistan Worker's Party (PKK).
"The supply of arms to the YPG is unacceptable," Deputy Prime Minister Nurettin Canikli told A Haber television.
"Such a policy will benefit nobody," he said. "We expect that this mistake is to be rectified."