President Donald Trump’s decision to withdraw U.S. troops from Syria won support from the top U.S. general in the region, although he warned Islamic State may try to reassert control and influence after losing its ability to hold territory in the war-torn country.

"If the major actors and their proxies become embroiled in a competition for influence in Syria, this may create space for ISIS remnants or other terrorist groups to reform or reconstitute," Gen. Joseph L. Votel, the head of U.S. Central Command, said in a report to the Senate Armed Services Committee on Tuesday.

The general offered that caution hours before Trump’s State of the Union address to Congress, in which the president may boast that the U.S. and allies have eliminated Islamic State’s “caliphate,” its hold on a huge swath of territory in Syria and Iraq. Votel effectively endorsed Trump’s pledge to withdraw U.S. troops from Syria, although he emphasized a methodical approach.

"We are adjusting our military posture in Syria, planning and executing a deliberate, safe, and professional withdrawal of personnel and equipment while preserving sufficient power in the region to ensure that we can continue to destroy remnants of ISIS fighters and ensure it does not return," he said in the report issued as he began testimony before the Senate panel.

The death of four Americans in a terrorist strike in Syria intensified the debate in Washington about Trump’s plans to pull American troops from Syria, where they’ve been fighting with Kurdish allies against Islamic State since 2015.

Despite Islamic State's territorial defeat, the president's allies have raised objections to the decision to withdraw American forces from Syria. Senate Majority Leader Mitch McConnell has said Islamic State and al-Qaeda weren't defeated yet and American national security interests require continued commitment. Republican Senator Lindsey Graham of South Carolina said the U.S. should slow down its planned exit to make sure Iran doesn't emerge as the biggest winner.

Defense Secretary Jim Mattis resigned over the withdrawal plan, and other officials have pushed back, creating confusion over the timetable. Mattis cited the importance of supporting the coalition of nations that united against Islamic State.

In a wide-ranging report on Central Command's challenges in the Middle East, Votel also noted Saudi Arabia's reduced influence.

“High-profile civilian casualty incidents on behalf of the Coalition in Yemen and international backlash resulting from the murder of Saudi dissident Jamal Khashoggi have damaged Saudi Arabia’s international standing,” he said.