Washington( CNN) House Judiciary Chairman Jerry Nadler on Sunday said Robert Mueller's report presents “very substantial evidence” that President Donald Trump is “guilty of high crimes and misdemeanors” — an impeachable offense.

Mueller, the former special advise for the Department of Justice and former director of the FBI, will testify before Congress on July 24 after House Democrats issued a subpoena for his appearance. Earlier this year, Mueller concluded a nearly two-year-long investigation into Russian interference in the 2016 presidential election.

Democrats are deeply divided on whether to pursue an impeachment investigation, and Mueller's public testimony may provide an opportunity for the party to unify and decide whether impeachment proceedings should go forward or not. More than 80 House Democrats have called for begin an impeachment inquiry into the President — the first step in a lengthy process, but House Speaker Nancy Pelosi and Nadler have so far resisted the pressure to open an inquiry. Behind the scenes, Nadler has lobbied Pelosi to open an inquiry.