Trump expected to retain attorney for Russia inquiry Marc Kasowitz has represented Trump in other matters for 15 years.

 -- President Donald Trump is expected to retain lawyer Marc Kasowitz as his private attorney representing him on matters related to the Russia investigation being led by Special Counsel Robert Mueller, a source close to Kasowitz and sources familiar with the Trump’s decision confirmed to ABC News.

Mueller was appointed by Deputy Attorney General Rod Rosenstein last week to lead the investigation into interference in the presidential election and any possible collusion with the Trump campaign. Mueller, a 12-year director of the FBI, was selected a week after his successor James Comey was fired by Trump, who later admitted he was thinking about the bureau's inquiry into the matter when he took action on Comey.

Kasowitz has represented Trump "on a wide range of litigation matters for over 15 years" according to his biography on his law firm's webpage. The firm, Kasowitz Benson Torres LLP, publicizes a number of its partner's representations of the president on its website, including in the restructuring of business debt, defamation cases and the effort to keep Trump's divorce records sealed as he campaigned last year.

The firm also employs former Senator Joe Lieberman as senior counsel, whom Trump said last week was his top choice to follow Comey as FBI director, though no nomination has yet been made.

The White House has not yet responded to a request for comment.