Turkish President Recep Tayyip Erdogan has said he hopes the United States will reverse its decision to arm Syrian Kurdish fighters perceived as terrorists by Ankara.
Mr Erdogan's remarks came a day after the US announced it would arm the fighters as a necessary step to recapture the Islamic State group's Syrian stronghold of Raqqa.
Mr Erdogan said the "fight against terrorism should not be led with another terror organisation" and that "we want to know that our allies will side with us and not with terror organisations".
The president said he would take up the issue during a planned meeting with US President Donald Trump on May 16.
Mr Erdogan said: "I hope that they (the US) will turn away from this wrong."
During a visit to Montenegro on Wednesday, Turkish foreign minister Mevlut Cavusoglu said there was no difference between the Syrian Kurdish fighters and the outlawed Kurdish rebels fighting Turkey.
"Every weapon that reaches their hands is a threat towards Turkey," Mr Cavusoglu said.
However, the Syrian Kurdish group labelled a terror organisation by Turkey hailed the US decision to arm it with heavy weapons to fight IS.
The YPG militia said the decision is "historic" and a "sign of confidence" in the group, in a statement released on Wednesday.
Turkey's deputy prime minister Nurettin Canikli denounced the decision as "unacceptable" and said it "amounts to support to a terror organisation".
"The Trump administration providing arms to a terrorist organisation - either directly or indirectly through the YPG - does not change the fact that this amounts to support to a terror organisation," Mr Canikli said.
The YPG said the US commitment to the group, and its umbrella coalition the Syrian Democratic Forces, will allow it to expand its operations against IS.
It said the decision is a refutation of the "distortions" likening the YPG to a terror organisation.
Ilham Ahmed, a top official in the Syrian Democratic Forces' political office, said the decision to provide heavier arms carries "political meaning" and "legitimises the YPG and the Syrian Democratic Forces".
She said the decision is likely to be met with "aggression" from Mr Erdogan.
The SDF's rapid advance against IS last year prompted Turkey to send ground forces across the border for the first time in the six-year civil war to help allied Syrian forces battle IS and halt the Kurds' progress.
Since then, Turkey is believed to have positioned more than 5,000 troops in northern Syria, and has escalated its air strikes and cross-border artillery attacks against Kurdish forces.
A Turkish air raid in late April killed 20 YPG fighters and media officials, prompting the US to deploy armoured vehicles along the border in a show of support for the group.