PHOENIX -- Sen. John McCain, R-Arizona, who faced questions as the 2008 GOP presidential nominee about his birth abroad, is now posing the same question to Sen. Ted Cruz, R-Texas.

In an interview Wednesday on Phoenix radio station 550 KFYI's Chris Merill Show, McCain said he "doesn't know" whether Cruz's birth in Canada makes him eligible to be president. Cruz, whose father was born in Cuba, asserts that he is a U.S. citizen because his mother was an American.

"I know that came up in my race because I was born in Panama, but I was born in the Canal Zone which is a territory. Barry Goldwater was born in Arizona when it was territory when he ran in 1964," McCain said.

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McCain added that he was born on a U.S. military base, which he said is not the same as being born in Canada.

"That's different from being born on foreign soil. I think there is a question. I'm not a constitutional scholar on that, but I think it's worth looking into. I don't think it's illegitimate to look into it."

Asked if the Supreme Court might have to weigh in on the "natural born citizen" issue, McCain said, "It may be, that may be the case."

Talk about Cruz's situation resurfaced after Donald Trump started raising questions about it in an interview published Tuesday by The Washington Post.

Trump advised Cruz on Wednesday to go to court to clarify his status.

On Thursday, he tweeted that he was offering Cruz "free legal advice."