Turkish President Recep Tayyip Erdogan said he would not meet with US Vice President Mike Pence during his visit to Ankara to discuss .
"I am standing tall. I will not meet with them," he told Sky News on Wednesday, referring to Mr Pence and Secretary of State Mike Pompeo.
"They will meet with their counterparts. I will speak when Trump comes," he said.
Turkey has remained defiant against against Kurdish militants in Syria, raising tensions with Washington.
Battles raged in the key Syrian border town of Ras al-Ain as dawn broke on Wednesday, with Kurdish fighters trying to hold off the onslaught by Turkish-backed forces, now in its second week.
Turkish President Recep Tayyip Erdogan addresses members of ruling Justice and Development Party. Source: EPA
The fighting has triggered a flurry of diplomacy among major powers, with US President Donald Trump dispatching Mr Pence and Mr Pompeo to Turkey amid the greatest crisis in relations for decades between the NATO allies.
The Kremlin said it would host President Recep Tayyip Erdogan for a meeting with his Russian counterpart Vladimir Putin in the coming days, to ensure the operation does not turn into an all-out war between Turkey and Syria.
Russia has stepped into the void caused by Mr Trump's withdrawal of US troops from northern Syria, deploying patrols to prevent clashes between Syrian and Turkish forces.
Mr Trump - facing mounting criticism in Washington over his decision to pull 1,000 troops out of the conflict zone, as well as an unrelated impeachment inquiry - has hit back at Mr Erdogan, slapping sanctions on three cabinet officials and raising tariffs on Turkish steel.
Vice President Mike Pence speaks to reporters outside the White House. Source: AP
Mr Pence previously said he would meet with Mr Erdogan on Thursday and "voice the United States' commitment to reach an immediate ceasefire and the conditions for a negotiated settlement", his office said in a statement.
He reiterated that Mr Trump will pursue "punishing economic sanctions" until a resolution is reached.
But Mr Erdogan has remained unfazed by the pressure, telling reporters: "They tell us 'to declare a ceasefire'. We can never declare a ceasefire."
The operation has widespread support in Turkey, where decades of bloody insurgency by Kurdish militants has killed tens of thousands of people.
But Western powers are spooked that the operation is endangering the battle against the Islamic State group, which was led on the ground by Kurdish forces. Thousands of IS prisoners are held in Kurdish-run camps in the region.
