Two Americans were among five ISIS fighters recently captured in eastern Syria, according to a spokesman for the U.S.-backed Syrian Democratic Forces.

The Americans were identified as Warren Christopher Clark (aka Abu Mohammad al-Ameriki) of Houston, and Zaid Abed al-Hamid (aka Abu Zaid al-Ameriki), originally from the U.S., but no specific location was reported.

Clark was identified in an NBC News report last February as an American who had sent his resume to ISIS, in hopes of joining the terror group.

“We are aware of open source reports of reportedly American citizens currently in custody who were believed to be fighting for ISIS," Navy Cmdr. Sean Robertson, a Pentagon spokesman, told Fox News in a statement. "However, we are unable to confirm this information at this time. The incident is under investigation."

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The three other fighters captured included one from Ireland and two from Pakistan, according to a Twitter message by Mustafa Bali, the SDF spokesman.

The fighters were captured as part of Operation Jazeera Storm, which is charged with liberating the last areas of Syria that remain under ISIS control, Bali’s statement said.

According to his account, ISIS is now cornered in a small area of the country after previously controlling a broad amount of territory before suffering heavy combat casualties.

As a result, ISIS has been plotting attacks against civilians trying to flee the war zone.

Meanwhile, the BBC reported that two British special operations soldiers were severely wounded in an ISIS attack in eastern Syria on Saturday.

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In December, President Trump said ISIS had been wiped out in Syria.

“We have defeated ISIS in Syria,” he wrote in a tweet.

But on Sunday in Jerusalem, John Bolton, national security adviser to President Trump, said the U.S. military withdrawal from northeastern Syria is conditioned on defeating the remnants of ISIS, and on Turkey assuring the safety of Kurdish fighters allied with the United States.

Bolton, who traveled to Israel to reassure the U.S. ally of the Trump-ordered withdrawal, said there is no timetable for the pullout of American forces in northeastern Syria, but insisted it’s not an unlimited commitment.

“There are objectives that we want to accomplish that condition the withdrawal,” Bolton told reporters. “The timetable flows from the policy decisions that we need to implement.”

Those conditions, he said, included the defeat of remnants of ISIS in Syria, and protections for Kurdish militias who have fought alongside U.S. troops against the extremist group.

Bolton’s comments mark the first public confirmation that the drawdown has been slowed, as Trump faced widespread criticism from allies and the resignation of Defense Secretary Jim Mattis for a policy that was to have been conducted within weeks.

Fox News' Lucas Tomlinson and the Associated Press contributed to this report.