Defense Secretary Jim Mattis told reporters on Tuesday that he has "no reservations, no concerns at all about working with" John Bolton when he becomes national security adviser next month.

Mattis said he has never met Bolton, but said he would form a partnership with the former U.S. ambassador to the U.N., even as he admitted Bolton's hawkish views might at times conflict with his own.

“I hope that there are some different worldviews. That’s the normal thing you want, unless you want groupthink,” Mattis said.

While Mattis has counseled President Trump to remain in the Iran nuclear deal and to pursue a diplomatically-led effort with North Korea, Bolton says the deal should be torn up and has said sanctions and diplomacy against North Korea have failed.

Bolton is scheduled to visit the Pentagon this week to meet with Mattis.

“We’re going to sit down together. I look forward to working with him,” Mattis said. "Last time I checked, he's an American. I can work with an American, OK?"