Nearly a week since U.S. President Donald Trump fired national security adviser Michael Flynn, U.S. Sen. Rand Paul advised against appointing former U.N. Ambassador and White House Chief of Staff John Bolton.

Trump’s first choice, retired Navy special forces officer Robert Harward, who served under Defense Secretary John Mattis, turned down the position last week and reports say the White House has ruled out former CIA Director David Petraeus, who was ousted as the nation’s top spy amid a scandal over his sharing confidential documents with his mistress.

Flynn resigned last week amid questions on whether he discussed sanctions with Russian Ambassador Sergey Kislyak.

Trump is scheduled to meet Sunday with four possible replacements: Bolton, retired Army Lt. Gen. Keith Kellogg, who is acting national security adviser, Army Lt. Gen. H.R. McMaster and the superintendent of the U.S. Military Academy at West Point, Lt. Gen. Robert Caslen. White House spokesman Sean Spicer said other interviews also could be scheduled.

In an interview on ABC’s “This Week,” Paul, R-Ky., a Libertarian who lost the 2016 Republican presidential nomination to Trump, said Bolton would push a foreign policy closer to that of Sen. John McCain,” R-Ariz.

“John Bolton still believes the Iraq war was a good idea, he still believes regime change is a good idea, he still believes that nation building is a good idea,” Paul said, adding, “My fear is that s secret wars would be developing around the globe. … I think he would be a bad choice.”

On NBC’s “Meet the Press,” White House Chief of Staff Reince Priebus said he is “fully aware” of the facts that led up to Flynn’s ouster after less than a month on the job.

“Some point after we were first tipped off and got to the point of reviewing whether he was being honest or not, after we got the report back from the White House counsel, that's when we looped in, or that's when the vice president was brought into the conversation more fully in regard to whether or not Michael Flynn was honest,” Priebus said.

Priebus added, however, he didn’t think Flynn’s actions rise to a criminal violation of the Logan Act, which prohibits private citizens from engaging in foreign policy.

Former CIA Director Leon Panetta, who served as Hillary Clinton’s campaign chairman, said Trump needs to recognize that Russia is “an adversary, not a friend.”

“Their main purpose is to destabilize the United States and Western democracies. And they've shown that in everything they've done. So the president, I think ultimately must recognize that his first responsibility is to protect this country. And one of those you have to protect this country from is Russia,” Panetta said on “Meet the Press.”