The United States has around 1,000 troops in Syria tackling Islamic State militants. Turkey has also launched military incursions into northern Syria, targeting Islamic State and Kurdish YPG fighters, according to Reuters.
“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.
US President Donald Trump last year ordered the complete withdrawal of US troops from Syria - only to later be convinced to leave some forces behind to ensure that Islamic State militants cannot stage a comeback.
The US intervention in Syria began with air strikes in September 2014 under Trump’s predecessor Barack Obama.
While Syria did not approve a US presence there, the Obama administration justified the military action under Article 51 of the UN Charter, which covers the individual or collective right of states to self-defense against armed attack.
“The United States and Turkey maintain an illegal military presence in northern Syria,” al-Moualem said, describing US and Turkish efforts to create a “safe zone” inside Syria as a violation of the UN Charter.
Turkey plans to build homes to settle 1 million Syrian refugees in the zone.
The United States and Turkey have started joint land and air patrols along part of Syria’s border with Turkey, but Ankara remains angry with Washington’s support for the YPG, which has been a key US ally in fighting Islamic State in Syria.
Western states have accused Russian and Syrian forces of targeting civilians in northwest Syria, a charge they deny. They say they are targeting militants.
“We are determined to continue our war against terrorism in all its forms until rooting out the last remaining terrorist,” al-Moualem said.
Reporter's code: 50101