It was not clear what letter President Donald Trump was referring to. | Chip Somodevilla/Getty Images Trump blasts Clapper, who questioned his fitness for office

President Donald Trump on Thursday attacked former national intelligence director James Clapper, who earlier this week questioned Trump’s fitness for office.

“James Clapper, who famously got caught lying to Congress, is now an authority on Donald Trump. Will he show you his beautiful letter to me?” Trump tweeted, referencing Clapper’s testimony before Congress in 2013 in which he said intelligence officials did not “wittingly” collect data on Americans.


It was not clear what letter he was referring to.

Clapper laced into Trump following his divisive speech at a Tuesday night rally in Phoenix, telling CNN, “I really question his ability to be — his fitness to be — in this office.”

“I also am beginning to wonder about his motivation for it — maybe he is looking for a way out,” Clapper added.

Clapper has been a frequent critic of Trump’s, but his comments early Wednesday morning dramatically escalated his rhetoric.