White House chief of staff John Kelly, who will depart President Donald Trump's administration on Wednesday, told The Los Angeles Times in an extensive interview published Sunday that the president never ordered him to do anything illegal and added that the proposed border wall at the center of the government shutdown fight is not as it has been portrayed.

Kelly, set to be replaced by Office of Management and Budget Director Mick Mulvaney, who will serve as acting chief of staff, said he made sure the president had access to detailed information prior to making decisions, even though the president says publicly that he goes with his gut instinct.

"It’s never been: The president just wants to make a decision based on no knowledge and ignorance,” Kelly said. “You may not like his decision, but at least he was fully informed on the impact."

White House Chief of Staff John Kelly listens as President Donald Trump speaks during a meeting with newly elected governors in the Cabinet Room of the White House on Dec. 13, 2018. Evan Vucci / AP

The retired Marine general said Trump often pressed him on his legal authority to do certain actions, asking, "Why can't we do [something] this way?" Kelly added that he was not ordered to carry out any illegal action "because we wouldn't have."

"If he had said to me, 'Do it, or you’re fired,'" Kelly insisted he would have resigned, later adding that he told Trump that "the last thing in my view that you need in the chief of staff is someone that looks at every issue through a political lens."

Pointing to Trump's pledge to build a massive wall along the U.S. border with Mexico — a central campaign promise — Kelly said, "To be honest, it's not a wall," meaning that Trump no longer is calling for a huge concrete structure spanning thousands of miles.

"The president still says 'wall' — oftentimes frankly he’ll say 'barrier' or 'fencing,' now he’s tended toward steel slats," Kelly said. "But we left a solid concrete wall early on in the administration, when we asked people what they needed and where they needed it."

Kelly, who said the country does "have an immigration problem," took aim at former Attorney General Jeff Sessions, blaming him for the administration's policy of family separation at the border. That policy led to hundreds of migrant children being split from their parents by U.S. authorities.

The policy announcement took the White House by surprise, the former Homeland Security secretary said.

"What happened was Jeff Sessions, he was the one that instituted the zero-tolerance process on the border that resulted in both people being detained and the family separation," Kelly said. "He surprised us."

The administration had earlier insisted there was no policy of separating families at the border.

On his way out, Kelly said his tenure as chief of staff could be evaluated not by what Trump did during that time, but rather what the president had not done.