Syria's foreign ministry on Sunday condemned a surprise visit by the United States' top military officer to an army base in the Kurdish-held northeast, dubbing it "illegal", state media said.
In his snap visit Saturday, Chairman of the Joint Chiefs of Staff General Mark Milley met US troops stationed in areas of war-torn Syria under the control of the Kurdish-led Syrian Democratic Forces (SDF).
About 900 US troops are deployed in several bases and posts across northeastern Syria as part of the fight against Islamic State group remnants.
Official news agency SANA quoted a foreign ministry official as saying "Syria strongly condemns the illegal visit of the American chairman of the chiefs of staff to an illegal American military base in northeast Syria."
Milley's visit was "a flagrant violation of the sovereignty and integrity" of Syrian territory, the official added according to SANA, calling on "the US administration to immediately cease its systematic and continued violation of international law and support for separatist armed groups".
President Bashar al-Assad's government views the deployment of US forces in SDF-held territory as "occupation" and accuses US-aligned Kurdish forces of "separatist tendencies".
Kurdish officials deny any separatist aspirations and say they seek to preserve their self-rule, which Damascus does not recognise.
Milley's spokesman, Dave Butler, told AFP the US general "visited northeast Syria Saturday... to meet with commanders and troops".
It was Milley's first trip to Syria since assuming the chairmanship in 2019. He visited the country before as an army chief, the spokesman said.
During the visit, Milley "received updates on the counter-ISIS mission", Butler added using an alternative acronym for the IS jihadists.
The general also "inspected force protection measures and asserted repatriation efforts for the Al-Hol refugee camp", home to more than 50,000 people, including family members of suspected foreign IS militants whose home countries have not taken them back.
The US-led coalition battling IS provides support for SDF, spearheaded by the Syrian Kurdish People's Protection Units (YPG).
After the jihadists lost their last territory to SDF-led forces in 2019, SDF has cracked down on remnants of IS, whose members still launch deadly attacks in Syria.
US forces have killed or arrested IS figures in numerous operations, including the group's leader Abu Bakr al-Baghdadi in 2019.
On February 19, the US military said troops working with SDF captured an IS provincial official.
The raid came a day after four US troops were wounded as they conducted another raid to kill a senior IS group leader in northeastern Syria, the US military's Central Command said.