US Vice President Mike Pence traveled to Ankara on Wednesday along with Secretary of State Mike Pompeo and other delegates to try and negotiate a settlement to the conflict. Pence will also reiterate the US' commitment to reaching an immediate ceasefire.

Pence will hold a bilateral meeting with Turkish President Tayyip Erdogan on Thursday where he will remind the Turkish president of the sanctions imposed until a resolution is reached.

On Tuesday, Erdogan told US President Donald Trump that he will never declare a ceasefire in northeastern Syria, according to reports by broadcaster NTV.

He also added that he was not worried about US sanctions over the ongoing offensive in the region.

Speaking to reporters on a flight back from Azerbaijan, Erdogan said talks with Washington and Moscow on Syria's Kobani and Manbij towns had continued, and added that it was "not negative" for the Syrian army to enter Manbij as long as militants in the area were cleared.

He also said he told Trump that Turkey would "not negotiate with a terrorist organisation" in response to Trump's mediation offer.

Separately, the Turkish presidency said on Tuesday that Erdogan told Russian President Vladimir Putin in a phone call that Turkey's incursion into northeastern Syria would contribute to counter-terrorism efforts, Syria's territorial integrity, and a political solution process.