Trump, a Republican, "sees himself as above the law," said Judiciary Committee Chairman Jerrold Nadler.
"We must be clear, no one, not even the president, is above the law." Democrats accuse Trump of abusing the power of his office by withholding aid to Ukraine, a vulnerable U.S. ally facing Russian aggression, as well as dangling a possible White House meeting to get Ukrainian President Volodymyr Zelenskiy to launch a probe of a Democratic political rival in the 2020 presidential race.
Trump has denied wrongdoing and calls the inquiry a hoax.
The White House has refused to participate in the hearings in the House because it says the process is unfair.