Turkish President Recep Tayyip Erdogan has rejected a US call for an immediate ceasefire in northern Syria.
Mr Erdogan’s comments come ahead of a visit to Turkey by the US vice-president and secretary of state.
Turkey launched an offensive targeting Syrian Kurdish fighters last week after US troops allied to them pulled out.
Russia, which backs Syria’s government, has meanwhile said it is trying to prevent clashes between the Turkish and Syrian armies in the region.
After four days of fighting, the Kurds agreed a deal with the Syrian government for the Syrian army to be deployed along the border to help repel the Turkish assault.
Turkey considers the Kurdish militia that leads the Syrian Democratic Forces (SDF) alliance a terrorist organisation and wants to push it away from the frontier.
Ankara also says it wants to create a “safe zone” reaching about 30km (20 miles) into Syria, where up to two million Syrian refugees currently living in Turkey could be resettled.
Critics of the Trump administration say the withdrawal of US troops from the region gave Turkey a “green light” for the offensive.
The US has repeatedly denied this, and on Monday Washington announced sanctions on Turkish ministries and senior government officials.
Dozens of civilians have reportedly been killed in the operation so far and at least 160,000 have fled the area, according to the UN.
On Tuesday, the medical charity Médecins Sans Frontières (MSF) said it had “taken the difficult decision to suspend the majority of its activities and evacuate all its international staff from north-east Syria”.