Rudy Giuliani suggested Sunday that President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE may not have to testify in special counsel's Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE investigation because of his tweets.

"A lot of his tweets have been very helpful. The reason he may not have to testify is that he’s laid out his defense very clearly," Giuliani said on CBS's "Face the Nation."

Giuliani, who is Trump's lead attorney in the Russia investigation, was responding to a New York Times report that Mueller is reviewing Trump’s tweets as he pursues an investigation into whether the president obstructed justice.

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The former New York City mayor also brushed aside the prospect that Trump's tweets could be used to build an obstruction case.

"Obstruction by tweet is not something I think works real well," Giuliani said.

"Generally obstruction is secret, it’s clandestine, it’s corrupt. I’ve looked at those tweets and they don’t amount to anything."

Has Giuliani told @realDonaldTrump to stop tweeting after reports Mueller is investigating the president’s tweets?@RudyGiuliani : Good luck about tweeting…Obstruction by tweet is something that doesn’t work so well. pic.twitter.com/O4utVBBqbY — Face The Nation (@FaceTheNation) July 29, 2018

The Times reported that Mueller is not focused on a single tweet or comment, but rather is using Trump's tweets to look at a larger pattern of behavior.

Mueller is particularly interested in Trump’s tweets about Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsRoy Moore sues Alabama over COVID-19 restrictions GOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs MORE, former FBI Director James Comey James Brien ComeySteele Dossier sub-source was subject of FBI counterintelligence probe Judge will not dismiss McCabe's case against DOJ Democrats fear Russia interference could spoil bid to retake Senate MORE and former FBI Deputy Director Andrew McCabe Andrew George McCabeJudge will not dismiss McCabe's case against DOJ Graham: Comey to testify about FBI's Russia probe, Mueller declined invitation Barr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' MORE, according to the Times.

The president has used the social media platform to fiercely criticize each official.

He fired Comey in May 2017, saying at the time it was because of the Russia investigation. He has offered conflicting explanations for the firing via Twitter.

Giuliani all but confirmed Sunday that the president's legal team has proposed to Mueller that Trump would agree to an interview only if questions about obstruction of justice were ruled out. Instead, the interview would focus on the issue of collusion, which the president has vehemently denied.