Otherwise, he said, "they have the right to take all the countermeasures allowed by international law."
Syrian Foreign Minister Walid al-Moualem demanded the "immediate withdrawal" of American and Turkish troops stationed within Syria's borders.
Speaking at the United Nations General Assembly, he said Syrian regime forces have the right to intervene if their demands are not met.
The United States has around 1,000 troops in Syria while Turkey has also launched military operations into northern Syria, targeting DAESH and YPG/PKK.
"Any foreign forces operating in our territories without our authorization are occupying forces and must withdraw immediately," al-Moualem said during an address to the annual gathering of world leaders at the United Nations in New York.
"If they refuse, we have the right to take any and all countermeasures authorized under international law," he said.
"The United States and Turkey maintain an illegal military presence in northern Syria," al-Moualem said, describing the US and Turkish efforts to create a "safe zone" inside Syria as a violation of the UN Charter.
ILKHA