Turkey has called on Kurdish fighters to leave its designated border zone in Syria on Wednesday night in order to end Ankara's offensive in the region.
Airstrikes continue to batter the region close to the Turkey-Syria border, while ground troops continue to push into Syria.
President Recep Tayyip Erdogan made it clear Turkey would not bow to pressure and would press ahead with the military operation until Turkish troops reach around 18 miles deep into Syria.
The Turkish leader has continually refused to give ground to Kurdish fighters, which Turkey deems as "terrorists".
He added he was not concerned about the presence of Syrian government troops moving into the city of Manbij, but that he wanted Kurdish fighters to leave the region.
US vice president Mike Pence is flying to Ankara to broker a deal between Kurdish and Turkish forces, although Erdogan said he would only discuss the offensive with Donald Trump.
The UN's special envoy for Syria said the world was "extremely alarmed by the humanitarian consequences of the crisis".
Geir Pedersen said there is only a political solution also to the crisis in the northeast and "we are appealing on all parties to participate in this".
He said it will work "as a door opener for the broader political process that is necessary to find a solution for the crisis in Syria".
Turkey's offensive began last week after US troops withdrew from the region, after their mission to combat the threat of ISIS was deemed to be completed.
Kurdish fighters had fought alongside US forces in the fight against ISIS, but the US withdrawal has been interpreted as a "stab in the back" for their efforts.
Russia has looked to fill the power vacuum along the Turkey-Syria border, pushing into key tactical strongholds previously held by US forces.
The Kurdish administration has struck a deal with Syria's Russian-backed president Bashar al-Assad, whose forces began moving into Kurdish-controlled regions to shield them against Turkey.
Moscow's envoy to to Syria, Alexander Lavrentyev told Russian state news that "no one is interested" in fighting between Syrian and Turkish forces, and that Russia "is not going to allow it".
Erdogan denied claims the country's offensive in northern Syria has targeted civilians.
He also said Turkey doesn't need a mediator and will not sit down at a table with the Kurdish fighters.