The United States has told Turkey that the YPG would not remain in the region after an operation on Syria's Raqqa, Turkish Prime Minister Binali Yildirim said on Friday.
Speaking to reporters in London where he is on an official visit, Yildirim said a US decision to provide weapons to the group in the fight against Daesh in Syria would harm the relations between the two NATO allies.
He said the United States had assured Turkey the region's demographics would not change as a result of this, a key concern for Ankara.
Turkey insists that the YPG is the Syrian branch of the PKK, which has waged war against the Turkish state since 1984.
Although both Turkey and the US consider the PKK to be a terrorist group, the US claims that the YPG has no connection with the PKK, in spite of considerable evidence.
Last week, the Pentagon announced that US President Donald Trump had approved arming what it called "Kurdish elements" of the Syrian Democratic Forces (SDF), a group dominated by the YPG.
This caused alarm in Turkey, which has long urged the US to proceed with the operation to liberate Raqqa from Daesh with the main Syrian opposition fighting faction, the Free Syrian Army (FSA) instead of the YPG.
Turkey's President Recep Tayyip Erdogan said on Wednesday that he would revisit the issue when he attends his first meeting with his US counterpart Donald Trump in Washington on May 16, but expects the US government to reverse its decision beforehand
Speaking again on Friday, Erdogan said his visit to the US could mark a "new beginning" in relations between the NATO allies while portraying Washington's decision to arm the YPG as a relic of the former Obama administration.
"The United States is still going through a transition period. And we have to be more careful and sensitive," he told a news conference in Ankara.
"Right now there are certain moves in the United States coming from the past, such as the weapons assistance to the YPG," Erdogan said.
"These are developments that are in contradiction to our strategic relations with the United States and of course we don't want this to happen."
Erdogan added that he did not want to see "a terrorist organisation alongside the United States," and that Turkey would continue military operations against YPG targets in Iraq and Syria regardless.
TRT World's John Joe Regan has more on the story from Gaziantep.
Elsewhere in Syria, hundreds of opposition fighters and their families left a besieged Damascus suburb on Friday as part of a local evacuation agreement with the regime.
They were the second group to leave the opposition-held Eastern Ghouta suburb under the deal, the first batch of evacuations from Barzeh having taken place on Monday.
The Syrian Observatory for Human Rights, a British-based war monitoring group, said about 700 people left the districts of Barzeh and neighbouring Tishreen on Friday, including about 150 fighters.
The towns and farms had been blockaded by regime forces since 2013.
Syrian regime leader Bashar al Assad has promoted the use of such evacuations, along with what his regime calls "reconciliation" deals for opposition-held areas that surrender to the regime.
The new initiative was taken to de-escalate the six-year war, having been brokered by Qatar and Iran.
However, the United Nations has criticised both the use of siege tactics which precede such deals and the evacuations themselves as amounting to forcible displacement.