Former National Security Advisor John Bolton knows about “many relevant meetings and conversations” connected to President Donald Trump pressuring Ukraine to launch a politically-motivated investigation, his lawyer said Friday.

In a letter to the House General Counsel, Bolton’s lawyer, Charles Cooper, wrote that his client would testify in the impeachment proceedings only if a court rules that he should ignore White House orders against it.

The House committee chairmen leading the impeachment effort have actively sought Bolton’s testimony.

Cooper said that Bolton did not show up for a deposition scheduled on Thursday because, he wants a judge to determine whether he and his former deputy and longtime ally, Charles Kupperman, should testify despite objections from the White House.

“Dr. Kupperman stands ready, as does Ambassador Bolton, to testify if the Judiciary resolves the conflict in favor of the Legislative Branch’s position respecting such testimony,” Cooper wrote.

He added, “If the House chooses not to pursue through subpoena the testimony of Dr. Kupperman and Ambassador Bolton, let the record be clear: that is the House’s decision.”

House lawmakers have withdrawn a subpoena for Kupperman and indicated they would not seek one for Bolton, because they said they did not want to get dragged into lengthy court proceedings.

A House Intelligence Committee official told them, “We regret Mr. Bolton’s decision not to appear voluntarily, but we have no interest in allowing the administration to play rope-a-dope with us in the courts for months.”

The lawmakers may choose to cite the refusal to testify by Bolton and Kupperman as evidence of obstruction of Congress by the president, since he is pressuring witnesses to defy subpoenas.

Bolton has been placed in the center of the impeachment inquiry, having had direct contact with the president and been name-dropped by several other witnesses.

William Taylor, the top U.S. envoy to Ukraine, said in his prepared opening statements that Bolton was “irritated” over efforts to pressure Ukraine to launch an investigation in exchange for an Oval Office meeting.

Taylor added, “Ambassador Bolton opposed a call between President [Volodymyr] Zelensky and President Trump out of concern that it ‘would be a disaster.'”

SLIDESHOW: TOP DEMOCRATS RUNNING FOR PRESIDENT IN 2020

Fiona Hill, who served as the top Russia policy specialist on the National Security Council, testified that Bolton called the arrangement with Ukraine a “drug deal” and warned that Trump’s personal attorney helping facilitate the plan, Rudy Giuliani, was a “hand grenade” that threatened to explode and hurt those around him.

Cooper’s letter acknowledges Bolton had a role, writing that he “was personally involved in many of the events, meetings, and conversations about which you have already received testimony, as well as many relevant meetings and conversations that have not yet been discussed in the testimonies thus far.”