(CNSNews.com) – Chairman of the Joint Chiefs of Staff Gen. Mark Milley paid a surprise visit to U.S. troops in Syria at the weekend, drawing criticism from both the Assad regime and a libertarian lawmaker at home who wants the administration to end their presence there.

Milley visited a base in northeast Syria where U.S. forces are stationed in a mission designed to prevent the resurgence of ISIS, the Sunni terrorist group that seized control over parts of Syria and Iraq almost a decade ago until largely defeated by 2019.

Around 900 U.S. troops remain in Syria, partnering with the Kurdish-led Syrian Democratic Forces (SDF) in a campaign to degrade the ability of ISIS’ scattered remnants to reemerge as a serious threat.

The Assad regime, which lost control over large areas of the country during the still-unresolved civil war but still claims to be the legitimate government over all of Syria, says the U.S. troops are uninvited and unwanted.

A foreign ministry official slammed Milley over the visit, and repeated a long-held claim by the regime and its allies, notably Iran and Hezbollah, that ISIS is in fact a U.S. creation, established to weaken its Mideast foes and sow divisions among Muslims.

“The U.S. chairman of the chiefs of staff made an illegal visit to an illegal U.S. military base in northeast Syria, and claimed that the reason for this visit was to assess the effectiveness of the war against Da’esh organization [ISIS],” the regime’s SANA news agency quoted the unnamed official as saying.

“However, the international community knows very well that Da’esh is an illegitimate offspring of U.S. intelligence.”

The official charged that U.S. support for “terrorist and separatist militias” in the area aims to prolong the war against Damascus, “for goals that are no longer hidden from anyone.”

“Syria strongly condemns this flagrant violation by the U.S. military official of the sovereignty and territorial integrity.”

The U.S. Congress never authorized the deployment of U.S. troops for engagement in hostilities in Syria.

Last month Rep. Matt Gaetz (R-Fla.) introduced a War Powers resolution aimed at forcing the administration to withdraw the troops. The measure will come up for a vote next week.

Gaetz on Sunday criticized Milley’s visit, which he said sought to “justify America’s continued involvement in a Middle Eastern civil war.”

“Jeffersonian Democracies cannot be built out of sand and blood and Arab militias alone,” he said. “Syria is a quagmire of a tinderbox. America has no discernible interest in continuing to fund a fight where alliances shift faster than the desert sands.”

Noting that his legislation comes up for a vote soon, Gaetz said that if Milley “wants this war so bad, he should explain what we are fighting for and why it is worth American treasure and blood. An America First foreign policy demands realism, rational thought, and seriousness.”

Gaetz introduced the resolution shortly after four U.S. military personnel and a working dog were injured during a helicopter raid in northeastern Syria with SDF partners against a high-ranking ISIS leader, who was killed in the operation.

Gaetz said at the time he introduced the measure that the U.S. was not at war with Syria, “so why are we conducting dangerous military operations there?”

“President Biden must remove all U.S. armed forces from Syria. America First means actually putting the people of our country first – not the interests of the military industrial complex.”

Reuters quoted Milley as telling reporters traveling with him that keeping the troops in Syria was worth the risk, citing the security of the U.S. and its allies.

“If you think that that’s important, then the answer is ‘Yes,’” he said. “I happen to think that’s important.”

Convoluted conflict

The Syrian civil war is a convoluted conflict that has drawn in several regional powers, adding to complications for U.S. troops stationed there.

Russia, the Assad regime’s key ally, accuses the U.S. of keeping troops in the country to retain its “sphere of influence” and exploit Syria’s natural resources.

The U.S. partnership with the SDF is bitterly opposed by Turkey – a NATO ally – which regards the Kurdish militiamen at the core of the SDF as terrorists due to their affiliation with Ankara’s key foe, the separatist Kurdistan Workers’ Party (PKK). Turkey continues to threaten new cross-border offensives against the Kurds.

The Iranian involvement adds another element of uncertainty.

While the main U.S. presence in Syria is in the northeast, a small number of personnel are also based several hundred miles to the south in Tanf, where the Syrian, Jordanian and Iraqi borders meet.

U.S. troops there have come under fire from Iranian proxy groups, most recently in a January drone attack that injured two members of an allied Syrian militia.

“U.S. forces are in Iraq and Syria to prosecute the defeat ISIS mission, working with partners on the ground,” Dana Stroul, Deputy Assistant Secretary of Defense for the Middle East, told a briefing in Riyadh last month. “We’re there for no other purpose.”

“Our forces are under constant threat from Iranian-aligned militia groups who seek to constantly harass our forces,” she said, in reference to the drone attack in Tanf.

Stroul said attacks by Iranian proxies undermine “our ability to continue prosecuting the defeat ISIS mission.”

“It also directly undermines, threatens, and jeopardizes the recovery efforts of those local communities who, only a few years ago, were under ISIS caliphate rule, experiencing the worst depravities and atrocities.”