The special counsel Robert Mueller is reportedly looking into whether President Donald Trump's tweets could open him up not only to obstruction of justice, but a potential witness tampering charge.

Mueller is reportedly focusing specifically on Trump's tweets about Attorney General Jeff Sessions and former FBI Director James Comey.

Trump's lawyers are said to be worried that Mueller's team is centering its obstruction case around a consistent pattern of behavior on Trump's part that could point to attempts to obstruct justice or influence witness testimony.

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President Donald Trump's critical tweets about Attorney General Jeff Sessions and former FBI Director James Comey could open him up to a possible witness tampering charge under a broad obstruction of justice law.

The New York Times reported Thursday that the special counsel Robert Mueller is interested in questioning Trump about his tweets and private interactions with Sessions and Comey to determine not only whether Trump sought to obstruct justice, but whether he tried to use his power to influence potential witnesses, three people briefed on the matter told the outlet.

Mueller's obstruction case stems from the president's decision to fire Comey last May. The White House initially said Comey was fired because of the way he handled the FBI's investigation into Hillary Clinton's use of a private email server. But Trump later said on national television that "this Russia thing" was a factor in his decision.

Comey testified to the Senate Intelligence Committee in June that Trump asked him for his loyalty during a private meeting in January, shortly after he took office. The former FBI director also said the president asked him to let go of the FBI's investigation into former national security adviser Michael Flynn.

Sessions, meanwhile, became the target of Trump's fury when he decided to recuse himself from the Russia investigation last March, after it surfaced that he failed to disclose his Russia contacts to Congress during his confirmation hearing.

Trump's frustration with the attorney general reached a boiling point last summer because he reportedly felt like Sessions was not doing enough to protect him from what he often characterizes as the Russia "witch hunt." He also accused Sessions of not investigating then-FBI deputy director Andrew McCabe's ties to Hillary Clinton.

Rudy Giuliani, Trump's lead defense lawyer, argued that Trump was within his rights to fire Comey and criticize Sessions.

"If you're going to obstruct justice, you do it quietly and secretly, not in public," Giuliani told The Times.

But the report said that Trump's legal team is growing increasingly concerned Mueller's obstruction case will hinge on showing a consistent pattern of behavior on Trump's part — using his tweets, private interactions, and other statements — pointing to obstruction of justice and potential witness tampering.

Trump has made several public and private statements that experts say could land him in jeopardy in the Russia probe.

Those actions involve, among other things:

Reportedly pressing Sessions to reverse his recusal at least four times.

Suggesting Sessions' recusal was a "betrayal."

Asking why "my guys" at the "Trump Justice Department" weren't doing more to shield him from Mueller's scrutiny.

Pressuring Comey, when he was FBI director, to publicly exonerate him in the Russia investigation.

Putting together a draft letter — which was not ultimately sent — laying out his reasons for firing Comey.

Publicly and privately musing about firing deputy attorney general Rod Rosenstein, who is overseeing Mueller.

Reportedly attempting to push top intelligence officials, including Director of National Intelligence Dan Coats and then CIA Director Mike Pompeo, to pressure Comey to back off from the Russia investigation.

Telling Russian government officials the day after Comey's firing that his dismissal had taken "great pressure" off of Trump.

Suggesting Comey should be investigated for rigging the FBI's investigation into Hillary Clinton's use of a private email server.

Reportedly ordering the White House counsel, Don McGahn, to fire Mueller. Trump backed off this request when McGahn threatened to resign.

Trump's lawyers appear to be aware of his vulnerability on the obstruction front. Earlier this week, The Times reported that the president's legal team is offering to allow Mueller to ask Trump about potential collusion — in exchange for curtailing his questions about obstruction.