Story highlights "If the President of the United States said that, he's got his reasons to say it," Kelly said

Kelly said he would expect Comey to turn Trump's wiretap allegation over to an investigative arm

Washington (CNN) Secretary of Homeland Security John Kelly said that President Donald Trump must have "convincing evidence" for his allegation on Twitter that President Barack Obama ordered a wiretap of his phones during the campaign.

"I don't know anything about it," he told CNN's Wolf Blitzer on the Situation Room. "If the President of the United States said that, he's got his reasons to say it."

Kelly continued: "He must have some convincing evidence that took place. ... I don't pretend to even guess as to what the motivation may have been for the previous administration to do something like that."

Trump created an uproar when he took to Twitter on Saturday to declare, without evidence, that Obama had the "wires tapped" in Trump Tower ahead of the election. The White House has declined to substantiate the President's claims, and a White House official told CNN that the theory reached Trump due to a Brietbart article circulating in the West Wing.

White House press secretary Sean Spicer, speaking at the White House on Monday, did not offer evidence to back up the claims, but doubled-down, saying, "There's no question that something happened."

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