President Donald Trump must provide the American people, not just the Senate Intelligence Committee, with proof of his claims that former President Barack Obama wiretapped Trump Tower, and if he doesn't have the proof, he needs to retract his statements, Sen. John McCain said Sunday.

"If his predecessor violated the law, President Obama violated the law, we've got a serious issue here, to say the least," McCain told CNN's "State of the Union" program, while pointing out that he himself has no reason to believe the allegations are true.

"I also believe that the president of the United States could clear this up in a minute," said the Arizona Republican. "All he has to do is pick up the phone, call the director of the CIA, the Director of National Intelligence and say, 'okay, what happened?' Because they certainly should know whether the former president of the United States was wiretapping Trump Tower."

When asked if he has any concern about Trump's "barrage of conspiracy theories" of Obama and others, McCain said Trump has a "unique style" and as he's the elected president, he's not going to tell him how to conduct his presidency.

"On an issue such as this, accusing a former president of the United States of doing something not only illegal but unheard of, that requires corroboration. I'll let the American people be the judge," said McCain. "This is serious stuff, if true, or the allegation is left out there, it undermines the confidence the American people have in the government."

McCain also addressed the firing of U.S. Attorney Preet Bharara after Attorney General Jeff Sessions and the Justice Department on Friday sought the resignations of the Manhattan-based federal prosecutor and 45 other U.S. Attorneys appointed by Obama.

The action came after Trump and Sessions had both reportedly told Bharara that his job was safe, but McCain said it is not unusual for new administrations to come in and clean house.

"Elections have consequences," McCain said. "For people to complain about it are ignoring the history of new presidencies. And I think the president had every right to ask for their resignations."

It was also learned this week that former National Security Agency Director Michael Flynn had been working for Turkey while he was advising the Trump campaign. McCain said there are many things that trouble him already about the nation's relationship with Russia, but he does not know if Flynn's work with Turkey was part of that.

"I know that he was in Moscow and had dinner with Putin, and I'm not sure that in its face is wrong, but there continues to surface communications between not just General Flynn but other members of the Trump family...there are still a lot of questions to be answered and so far are not being answered."

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