Washington • Former White House counsel Donald McGahn was a no-show Tuesday at a House committee hearing, infuriating Democrats who are ramping up calls to start impeachment proceedings against President Donald Trump despite continued resistance from House Speaker Nancy Pelosi, D-Calif.

During an opening statement, House Judiciary Committee Chairman Jerrold Nadler, D-N.Y., vowed that his panel would eventually hear McGahn's testimony about alleged obstruction of justice by Trump "even if we have to go to court to secure it."

"We will not allow the president to block congressional subpoenas, putting himself and his allies above the law," Nadler said. "We will not allow the president to stop this investigation, and nothing in these unjustified and unjustifiable legal attacks will stop us from pressing forward with our work on behalf of the American people. We will hold this president accountable, one way or the other."

Tuesday was the second "empty chair" hearing this month held by the Judiciary Committee. Three weeks ago, Attorney General William Barr declined to appear.

The White House announced Monday that it would block McGahn from testifying, the latest act of defiance in the ongoing war between House Democrats and Trump.

Democrats hoped McGahn would become a star witness in their investigation into whether Trump obstructed justice, given he delivered critical testimony in several instances of potential obstruction by Trump detailed in the report by Special Counsel Robert Mueller.

A 15-page legal opinion written by Assistant Attorney General Steven Engel argued that McGahn could not be compelled to testify before the Judiciary Committee, based on past Justice Department legal opinions regarding the president's close advisers.

The memo said McGahn's immunity from congressional testimony was separate and broader than a claim of executive privilege.

During closed-door meetings Monday night, several members of Pelosi's leadership team pressed her to begin an impeachment inquiry against Trump, according to multiple officials in the rooms - an effort the speaker rebuffed each time.

At least five members of Pelosi’s leadership team — four of whom also sit on the House Judiciary Committee, with jurisdiction over impeachment — pressed Pelosi in a closed-door leadership meeting to allow the panel to start an inquiry, which they argued would help investigators attain documents and testimony that Trump has blocked.

Several hours later, Nadler met with Pelosi as well and made the case to start the inquiry, he later told his panel members on a call.

Pelosi declined to endorse the idea both times, according to the officials either in or familiar with what happened in both meetings. She and House Majority Leader Steny Hoyer, D-Md., argued that such an inquiry would undercut other House investigations - or that the idea was not supported by other members in the caucus.

The Washington Post’s Mike DeBonis, Josh Dawsey and Devlin Barrett contributed to this report.