A first consignment of weapons is already in place for delivery and could be dispatched to the Kurds "very quickly," said US Colonel John Dorrian, a military spokesman for the anti-Islamic State (IS) coalition in Baghdad.
The White House has already given the Pentagon the green light to deliver weapons to the Kurdish Peoples' Protection Units (YPG), a group of Kurdish fighters battling IS extremists.
The decision to arm the Kurds had already provoked anger in Turkey, which says the YPG are linked to its own domestic Kurdish separatist group the PKK, or Kurdish Workers Party.
The PKK has been waging a bloody armed campaign since 1994 that has left thousands of dead, and is deemed a terrorist organization by both Ankara and its western allies.
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Turkey fears weapons delivered to Syrian fighters could end up in the hands of the PKK and be turned on Turkish targets.
But the US insists the arms being delivered are carefully calibrated to the needs of an anticipated offensive against the main IS base in the Syrian town of Raqa, and that they will keep tabs on all the weapons being deployed.
"Every single one of these weapons that are being provided to our partner force, we intend to account for them, and to ensure that they are pointed at ISIS," said Dorrian, referring to the Islamic State group.
The US shipments will include heavy machine guns to be used against IS truck bombs, mortars, small arms and ammunition, as well as armored vehicles and equipment to detect landmines, Dorrian said.
The dispute over how best to tackle IS in Syria has soured ties between the two NATO allies during the past year.
Last month, Turkish warplanes bombed YPG positions in northeastern Syria, angering Washington.