WASHINGTON — U.S. troops will remain in Iraq years after the main fight against Islamic State group militants is over, the Defense Department's top leaders warned Wednesday.



Under questioning from the Senate, Defense Secretary James Mattis said he supports the idea of keeping a residual American military force in Iraq after the current battle for Mosul is complete. The city is seen as ISIS' last significant stronghold in the country.



"I believe it's in our national interest that we keep Iraqi security forces in a position to keep our mutual enemies on their back foot," Mattis said.



Joint Chiefs Chairman Gen. Joseph Dunford Jr. echoed that sentiment, noting that "the Iraqi security forces will need that kind of support for years to come."



The comments come the U.S. military campaign approaches its three-year anniversary, building from air strikes against the terrorist group in summer 2014 to about 6,000 ground forces currently deployed across Iraq and Syria. Another 2,500 have been moved to Kuwait as possible supplemental or reinforcement personnel for that fight.



Military officials have repeatedly emphasized that Iraqi forces remain in the lead in the fighting, with U.S. forces there to provide training and logistics assistance.





Some members of Congress have voiced concerns about the ever-growing U.S. presence there, and the possibility of another open-ended war in the Middle East.

But conservatives who opposed the full withdrawal of U.S. forces from Iraq in 2011 — after a new status of forces agreements could not be negotiated with the Iraqi government — have pushed for military commanders to have fewer restrictions on Pentagon decisions in the region.

So far, President Trump has signaled his support for military requests for more troops and strategic freedom in the region.

Mattis said told senators that even after the main campaign against ISIS fighters ends, "I don’t see any reason to pull out again and face the same lesson." Dunford said the United States "needs to remain decisively engaged in Iraq and in the region."

Both also signaled support for additional U.S. assistance for again rebuilding infrastructure in the war-torn country, which Iraqi government officials have estimated at $50 billion in coming years.

"It’s going to be an international effort, it should not be carried fully by the American taxpayer," Mattis said. "But we should certainly be part of it."

× Fear of missing out? Sign up for the Early Bird Brief - a daily roundup of military and defense news stories from around the globe. Thanks for signing up. By giving us your email, you are opting in to the Early Bird Brief.

In a meeting across town Wednesday, top U.S. officials including Secretary of State Rex Tillerson urged coalition partners to step up efforts in the fight against ISIS, discussing both long-term military strategy and post-fighting humanitarian and reconstruction assistance.

Leo Shane III covers Congress, Veterans Affairs and the White House for Military Times. He can be reached at lshane@militarytimes.com.