“Snitty.”

That’s the way Attorney General William Barr described a letter from special counsel Robert Mueller expressing concerns about his portrayal of the Russia probe.

WATCH: William Barr testifies on Mueller report to Senate committee

Barr was testifying at the Senate Judiciary Committee on Wednesday when Democrat Richard Blumenthal of Connecticut asked about the letter. Mueller wrote it March 27, but it was only disclosed publicly ahead of the hearing.

“The letter’s a bit snitty,” Barr said. He said he thinks it was probably written by someone on Mueller’s staff.

Barr said he called Mueller the next day and said: “What’s with the letter? Why don’t you just pick up the phone and call me if there was an issue?”

Blumenthal characterized the letter an “extraordinary act” of “rebuking the Attorney General of the United States” and “memorializing it in writing.”