California Senator Dianne Feinstein said that a Senate committee's investigation looking into Russia's influence in the U.S. election was also exploring a potential "obstruction of justice" charge against President Donald Trump, the Democrat told NBC on Sunday.

Feinstein, who is the ranking member of the Senate Judiciary Committee, said in an appearance on NBC's "Meet the Press" that group was "putting together of a case of obstruction of justice."

She added: "I think we see this in the indictments, the four indictments and pleas that have just taken place and some of the comments that are being made."

Feinstein's comments in the wake of former national security advisor Michael Flynn entering a guilty plea for lying to federal investigators about conversations he had with a Russian ambassador.

While Trump insisted on Saturday Flynn's conversations were "lawful" and above board, he acknowledged that he fired the former general for lying to investigators during the transition phase.