Chris Clark, a lawyer for Hunter Biden, threatened the U.S. attorney investigating his client that if his client was charged in the case, the defense would call President Joe Biden to testify, thus creating a constitutional crisis by pitting the president against his own Department of Justice, POLITICO reported.

The warning came after information had leaked to the news media that federal prosecutors believed they had enough information to charge Hunter Biden for illegally purchasing a firearm despite being a drug addict.

"President Biden now unquestionably would be a fact witness for the defense in any criminal trial," Clark said in a lengthy letter to prosecutors, later adding: "This of all cases justifies neither the spectacle of a sitting President testifying at a criminal trial nor the potential for a resulting Constitutional crisis."