The top U.S. military commander in the Middle East told reporters Saturday while touring military bases in Syria that the U.S. remains committed to its mission and will “be here for a while.”

Gen. Frank McKenzie said that operations against the Islamic State are on the rise again after the U.S. cut back due to the increased tensions with Iran and the need to concentrate on increasing security.

Gen. Frank McKenzie, center front, the top U.S. commander for the Middle East, walks as he visits a military outpost in Syria. (AP)

America's mission to train and partner with Syrian Democratic Forces in the fight against ISIS has been tested in recent months. Last year, President Donald Trump ordered U.S. troops to withdraw from Syria as part of his vow to bring forces home and halt the endless wars. But over time, military commanders, members of Congress and other leaders convinced Trump to keep a small force in Syria to protect an expanse of Kurdish-controlled oil fields and facilities from falling under the control of ISIS

McKenzie, who met with the SDF's commander, Mazloum Abdi, at a military base in eastern Syria Saturday morning, said the Kurdish leader wanted assurances that the U.S. would continue to help his fighters. He said he told Abdi that the U.S will continue to conduct anti-IS missions, partner with the rebel forces, and help protect the oil fields.

"He knows, and I agree, that we're not going to be here for 100 years," McKenzie said. "I frankly don't know how long we're going to be here, and I have no instructions other than to continue to work with our partner here."

The U.S. declared an end to ISIS’ physical caliphate last March. But in recent months, the insurgents have regrouped, particularly in the west where U.S. forces are not present.

Operations against ISIS were interrupted following a U.S. drone strike that killed Gen. Qassem Soleimani, Iran’s top military general in Iraq. In retaliation, Iran launched ballistic missiles at two military bases in Iraq where U.S. troops are stationed. Several dozen were diagnosed with traumatic brain injury, but no one was killed in the attacks.

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"Certainly, the pace of operations went down earlier in the year, based on events in Iraq," McKenzie told reporters. "We're now back up to, I think, probably three or four operations a week with our partners here — so that pace is beginning to pick up and we are very pleased with that."

Maj. Gen. Eric Hill, commander of the special operations forces in Iraq and Syria, said his forces continue to train and conduct operations with the SDF to root out ISIS insurgents who are "hiding in the valleys, in the caves, in the desserts, trying to regroup."

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There are now about 750 U.S. troops in eastern Syria, spread across a swath of land stretching more than 90 miles from Deir el-Zour to the border region east of al-Hassakeh.

The Associated Press contributed to this report.