Comey was so appalled by the request that he wanted to document it, sources said. Comey shared it with FBI senior officials, according to sources.
"I hope you can let this go," Comey wrote, quoting the President. CNN has not viewed the memo but sources described it to CNN.
The memo is the clearest sign yet of potential interference by Trump with the investigation into whether members of his campaign team colluded with Russian officials.
