By Ali Dukakis, ABC News–

Former Defense Secretary and CIA Director Robert Gates called it “a big mistake” by President Trump to downgrade the status of the director of national intelligence and the chairman of the Joint Chiefs of Staff on the National Security Council, limiting which council meetings the two leaders can attend.

Trump made the change to the National Security Council in an executive memorandum Saturday that also gave the president’s controversial senior adviser and chief strategist Stephen Bannon a seat at the council’s Principals Committee meetings.

“My biggest concern is there are actually, under the law, two statutory advisers to the National Security Council, and that’s the director of

[national] intelligence, or the DNI, and the chairman of the joint chiefs of staff,” Gates told ABC News’ Martha Raddatz on “This Week.” “They both bring a perspective and judgment and experience … that every president — whether they like it or not — finds useful.”

According to Saturday’s memo outlining the changes, both leaders will now only attend NSC Principals Committee meetings “where issues pertaining to their responsibilities and expertise are to be discussed.”

“Pushing them out of the National Security Council [Principals] meetings except when their specific issues are at stake is a big mistake,” said Gates, who served as Defense Secretary for both Presidents George W. Bush and Barack Obama.

As for Bannon, Trump’s controversial adviser and the former publisher of Breitbart News, Gates said that adding people to National Security Council meetings “never really bothers me.”

White House press secretary Sean Spicer defended giving Bannon a seat at the Principals meetings, saying the chief strategist’s role is going to be “crucial,” adding that Bannon is a former Naval officer who has “a tremendous understanding of the world and the geopolitical landscape that we have now.”

“Having the chief strategist for the president in those meetings who has a significant military background to help make — guide what the president’s final analysis is going to be is crucial,” Spicer said on “This Week.”

President Obama’s former national security adviser Susan Rice responded to the National Security Council changes this morning, calling it “stone cold crazy.”

“That’s clearly inappropriate language from a former ambassador,” Spicer responded on “This Week.”

“We are instilling reforms to make sure that we streamline the process for the president to make decisions on key, important intelligence matters,” he added. “What they have done is modernize the National Security Council so that it is less bureaucratic and more focused on providing the president with the intelligence he needs.”

Editor’s Note: An earlier version of this story indicated that under the president’s signed memorandum, the director of national intelligence and chairman of the Joint Chiefs of Staff would be limited in attending National Security Council meetings. As Martha Raddatz stated on “This Week,” it is the National Security Council Principals Committee meetings to which their attendance will be limited. In addition, White House chief strategist Stephen Bannon now also has a seat at National Security Council Principals Committee meetings.