Attorney General William Barr said special counsel Robert Mueller's letter to him challenging his summary of the Russia inquiry was a "bit snitty."

Testifying before the Senate Judiciary Committee on Wednesday, Barr also said the letter was likely written by one of Mueller's "staff people."

The special counsel's letter said Barr's summary "did not fully capture the context, nature, and substance of this Office's work and conclusions."

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Attorney General William Barr on Wednesday said the letter he received from special counsel Robert Mueller challenging his summary of the report on the Russia probe was a "bit snitty."

"The letter's a bit snitty and I think it was probably written by one of his staff people," Barr told lawmakers as he testified before the Senate Judiciary Committee on Mueller's report on Russian election interference.

Mueller submitted his report to Barr on March 22 and two days later the attorney general sent a four-page summary to Congress.

His summary said Mueller did not find sufficient evidence to conclude that the Trump campaign conspired with the Kremlin to interfere in the election. Barr also said that Mueller did not fully "exonerate" Trump on obstruction but also didn't "conclude that the President committed a crime."

Read more: Mueller wrote a letter to Attorney General Barr objecting to his conclusion that Trump did not obstruct justice in the Russia probe

Additionally, the attorney general said that he and Deputy Attorney General Rod Rosenstein had reviewed the report and determined there wasn't sufficient evidence to charge the president with obstruction of justice.

Mueller wrote a letter to Barr three days after the summary was delivered expressing consternation over the attorney general's characterization of his team's findings. The special counsel in the letter said Barr's summary "did not fully capture the context, nature, and substance of this Office's work and conclusions."

"We communicated that concern to the Department on the morning of March 25," Mueller added. "There is now public confusion about critical aspects of the results of our investigation. This threatens to undermine a central purpose for which the Department appointed the Special Counsel: to assure full public confidence in the outcome of the investigations."

The letter was first reported by The New York Times on Tuesday. The House Judiciary Committee obtained a copy of the document the next morning.

A redacted version of Mueller's report was released roughly two weeks ago. Barr has been heavily criticized over its rollout and some Democrats have called for his resignation. On Wednesday, the attorney general faced tough questions from Democratic lawmakers over the process surrounding the report's release.

A spokesperson for the special counsel's office declined to comment on the attorney general's Wednesday remarks.