Turkish President Recep Tayyip Erdogan said Sunday rifts remain in the way Turkey and the USA envision the zone, claiming Washington was "trying to create a safe zone for the terrorist organization, not for us".
Turkey's foreign minister, Mevlut Cavusoglu, told reporters in Ankara on Tuesday that there had been "only cosmetic" steps taken in establishing the buffer zone.
He was referring to the latest joint Turkish-U.S. helicopter patrols of the planned safe zone area, as well as a joint floor forces patrol that took spot on Sunday.
Turkey, which labels the YPG a terrorist organization, wants the operations to expand rapidly as far as 20 miles (32 km) from its border to create a zone controlled by Turkish troops.
Foreign Minister Mevlut Cavusoglu told journalists that Washington was too strongly involved with USA -allied Syrian Kurdish fighters and was stalling on plans for the safe zone.
North Atlantic Treaty Organisation allies have agreed to create a security zone in northeastern Syria along Turkey's southern border and to clear the area from Syrian Kurdish fighters.
The YPG is the Syrian offshoot of terror group PKK.
A USA military delegation visited the Turkish General Staff headquarters over a safe zone in Syria, according to the country's National Defence Ministry on Tuesday. "But, we are uncomfortable with the USA providing equipment and ammunition to these terrorists with nearly 50,000 trucks", he said.
The two countries agreed a road map in May 2018 to clear the YPG from Manbij in northern Syria, but Turkey says the withdrawal never happened as agreed.
Earlier, Turkish President Recep Tayyip Erdogan said that if the West does not contribute to the creation of a security zone in northern Syria, Ankara will open the borders of Turkey with Europe for Syrian refugees.
"Turkey's plans are ready", Cavusoglu said. Erdogan and Trump are due to meet on the sidelines of the United Nations General Assembly later this month to discuss developments in Syria, trade and other bilateral issues.