Turkey views YPG as an extension of Kurdistan Workers Party, which has fought a three-decade insurgency in Turkey and is considered a terrorist group by US, Turkey and EU.
"These steps are extremely unsafe in terms of Syria's national unity and border integrity". In northern Syria there is the SDF, the YPG, and Syria Arab Coalition - a group of Arab fighters incorporated into the SDF.
Kurdish fighters from the People's Protection Units (YPG) stand near a U.S military vehicle in the town of Darbasiya near the Turkish border, Syria April 28, 2017.
The US' weapons transfers began ahead of an upcoming offensive to recapture Raqa, the last major bastion for IS in Syria.
Turkey believes the Syrian Kurds are linked to the PKK (also known as the Kurdistan Workers' Party) which is recognized as a terrorist organization not only by Turkey, but also by North Atlantic Treaty Organisation, the United States, the European Union and by Israel.
A resident now in Turkey called Abu Mohammed, who is in contact with relatives there, said: "The situation is getting worse every day, especially since..."
During the almost three-month Turkish assault on the ISIS-held city of Bab in December, Turkish forces lost almost 11 tanks, three infantry fighting vehicles, and an armored personnel carrier, mostly to anti-tank weapons captured by ISIS fighters, according to an investigative report compiled by Bellingcat, an open source investigative journalism platform founded by Eliot Higgins, a senior fellow at the Atlantic Council.
USA -backed forces are roughly 3km (2 miles) away from Raqqa city, the former de facto capital of the so-called Islamic State (ISIS) in Syria, according to the United Kingdom-based monitor the Syrian Observatory for Human Rights.
"The president clearly expressed our position and concerns during his Washington visit". "These weapons could be used against all humanity, not just Turkey, " the Turkish FM added.
The U.S.is supplying affiliated rebel groups in southern Syria with more weapons and support, in light of a new push by Iranian proxies toward their area of operations, Reuters reported.