President Donald Trump inherited a "real mess" with Syria, but at the same time, Turkey should have worked with the U.S. government and Syria's Kurds to address the concerns of the Turkish people, Sen. Tom Cotton said Thursday.

"The situation is very complicated in Syria, made more complicated by years of inaction under the Obama administration," the Arkansas Republican told Fox News' "America's Newsroom," pointing out that when Trump took office in 2017, ISIS was still prominent in the region.

"We were working with good allies, the Syrian Kurds, that unfortunately were the sworn enemies of a NATO ally, Turkey," said Cotton. "What the president did earlier this month is to say we weren't going to put at risk the lives of a few dozen American troops in northern Syria when Turkey was preparing to cross the border to try to protect itself from what it views as the Syrian-based militia of a Turkey-based separatist and terrorist organization. Turkey ought not to have done that."

A cease-fire that was reached has held, partly because Trump imposed sanctions and because Congress was threatening more sanctions, said Cotton, but the United States has remaining interests — and troops — in parts of Syria.

The U.S. should be able to protect those interests through its troop presence in eastern Syria, said Cotton, but at the same time, Turkey's President Recep Tayyip Erdogan should know that the sanctions are still there.

Meanwhile, Secretary of Defense Mark Esper and Secretary of State Mike Pompeo have confirmed that the vast majority of ISIS prisoners are still being detained, with the exception of 100 who escaped from where they were being held near the Syria-Turkey border.

"I know the president has consulted with the general commander of the Syrian Democratic Forces and [they] committed to the president they will continue to guard those prisons and that they will work in consultation with the United States military presence in Syria, should that become a strain on their capabilities," said Cotton.

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