Washington (CNN) Former Director of National Intelligence James Clapper said Wednesday it was "both stunning and scary" that Attorney General William Barr would tell lawmakers that Donald Trump's 2016 campaign was spied on.

"I thought it was both stunning and scary," Clapper, who served under President Barack Obama, told CNN's Anderson Cooper. "I was amazed at that and rather disappointed that the attorney general would say such a thing. The term 'spying' has all kinds of negative connotations and I have to believe he chose that term deliberately."

Barr told lawmakers Wednesday that he would look into the FBI's counterintelligence investigation that began in 2016 of potential ties between members of Trump's presidential campaign and the Russian government.

"For the same reason we're worried about foreign influence in elections, I think spying on a political campaign is a big deal," Barr said. "I'm not suggesting those rules were violated but I think it's important to look at. ... I think it's my obligation."

A source familiar with Barr's thinking, however, said that he referred to "spying" in the "classic sense" of intelligence collection, not as "pejorative." The attorney general did not provide evidence of any spying.

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