Washington (CNN) John Paul Stevens -- an outspoken retired justice -- said he hoped President Donald Trump would not damage on the nation's courts "too much" and waved off nascent proposals by Democrats to add more seats to the Supreme Court.

"I hope he won't do too much damage," the retired liberal justice told CNN's John Berman.

Speaking in an interview that aired Tuesday on CNN's "New Day" as he releases a memoir, the 99-year-old former jurist sounded off on Trump's reshaping of the courts as well as a proposal that has gotten sign off from some Democrats to alter the balance of the Supreme Court.

"I don't think they should do that," Stevens said of court packing proposals. "I think in time the court will straighten itself out. It may take longer, but I don't think the answer is increasing the number of justices."

'Roberts was dead right' in response to Trump

One of the most significant areas of Trump's presidency has been the nomination and successful Senate confirmation of scores of federal judges for lifetime appointments, including two members of the Supreme Court.

Notably, the efforts have been championed by Senate Majority Leader Mitch McConnell and done with the advice of conservative advocates.

Stevens said while he would not have made the same judicial appointments as Trump, he thought Trump was "getting advice from people who are knowledgeable about judges." But when asked if Trump understood the role of the judiciary, Stevens responded flatly: "No."

"I think he often speaks about them as Obama judges and other kinds of judges," Stevens said. "But I think (Chief Justice) John Roberts was dead right when he said that there are only one kind of judges and they're all working for the federal government."

Stevens was referencing Trump's frequent criticism of judges as political actors, dismissing some appointees of President Barack Obama who have decided against him. The criticism landed Trump a rare rebuke from Roberts last year, to which Trump fired back at Roberts and doubled down on his remarks.

Stevens was appointed by President Gerald Ford, a Republican, and came to be regarded as a liberal member of the court. He stepped down during the Obama administration, and in his CNN interview, Stevens said he did not know if he was a Republican or not anymore.

"I can say I do not expect to vote for the Republican candidate for president at the next election," Stevens said. "I don't know whether I'm a member of the party or I'm not. I'm not active politically."

On two sitting justices

Stevens said during the Brett Kavanaugh confirmation last year there was "merit" to criticism that the Trump's nominee had demonstrated "potential bias." He called on senators to focus on the problem and suggested Kavanaugh should not be confirmed.

Of course, after the contentious hearings were through, the Senate voted to confirm Kavanaugh, who has since settled into his position on the nation's highest court.

Stevens told CNN that Kavanaugh was a "good judge" and had been doing a good job on the Supreme Court so far, but when asked if he regretted speaking out, Stevens said, "No, that's really an entirely separate issue."

"Perhaps I shouldn't have said what I did," he continued. "But I think his decisions will determine how good a judge he'll be."

Stevens said last year that his decision to step down came from when he suffered a "mini-stroke" while reading from the bench. Asked about any similar health considerations that have been brought up about liberal icon Justice Ruth Bader Ginsburg, Stevens said he understood those who want her to stay on the court until a Democrat again occupies the Oval Office.

"And I think she's really in better health than people generally assume, cause she's survived both cancer and a similar episode some years ago," Stevens said. "And she -- apparently, she has a trainer too."