Turkish President Recep Tayyip Erdogan has vowed to push forward with the cross-border operation against the Kurdish-run Afrin enclave in northern Syria that has raised concerns among many of Ankara's allies, report agencies.
Erdogan's comments came on Wednesday after a telephone call with US President Donald Trump, who urged the Turkish leader to "avoid any actions that might risk conflict between Turkish and American forces."
Turkey's air and ground operation in Syria's Afrin region, now in its fifth day, targets US-backed Kurdish YPG fighters, which Ankara sees as allies of Kurdish insurgents who have fought in southeastern Turkey for decades.
Turkish President Tayyip Erdogan said he would extend the operation to Manbij, a separate Kurdish-held enclave some 100 km east of Afrin, possibly putting US forces there at risk and threatening US plans to stabilise a swath of Syria.
Speaking with Erdogan by telephone, Trump became the latest US official to try to rein in the offensive and to pointedly flag the risk of the two allies' forces coming into conflict.
"He urged Turkey to deescalate, limit its military actions, and avoid civilian casualties," a White House statement said. "He urged Turkey to exercise caution and to avoid any actions that might risk conflict between Turkish and American forces."
The United States has around 2,000 troops in Syria.
However, a Turkish source said the White House statement did not accurately reflect the content of their phone call.
"President Trump did not share any 'concerns about escalating violence' with regard to the ongoing military operation in Afrin," the source said, referring to one comment in the White House summary of their conversation.
"The two leaders' discussion of Operation Olive Branch was limited to an exchange of views," the source said.
Trump said in response to Erdogan's call on the United States to end the delivery of weapons to the YPG that the United States no longer supplied the group with weapons and pledged not to resume the weapons delivery in the future, the source said.
The United States hopes to use the YPG's control of the area to give it the diplomatic muscle it needs to revive UN-led talks in Geneva on a deal that would end Syria's civil war and eventually lead to the ouster of President Bashar Assad.
A Kurdish official told the German dpa news agency that US soldiers are still in Manbij, bringing up the possibility of unintended clashes between the forces of the NATO allies.
"Starting with Manbij, we will destroy this game along our borders and completely cleanse our region of this mischief," Erdogan said, vowing to "exterminate the terrorists."
The Syrian government has condemned what it called "Turkish aggression on Afrin."
Meanwhile, violence continued in both Afrin -- formerly a relatively stable pocket amid the chaos of Syria's ongoing civil war -- and in a neighbouring region of Turkey, where rockets fired from Syria killed two people and wounded 11 more.
The rockets, one of which hit and damaged a mosque, were fired in the early evening in the border province of Kilis, an AFP correspondent at the scene said. The second fell on a house 100 meters (300 feet) away, Kilis Governor Mehmet Tekinarslan said.
One Syrian and one Turk was killed, the governor's office said, in attacks it blamed on the Syrian Kurdish People's Protection Units or YPG, a militia that Turkey sees as a Syrian offshoot of the banned PKK, which has waged a three-decade insurgency inside Turkey.
