ATLANTA — John Bolton, President Trump’s former national security adviser, knows about “many relevant meetings and conversations” connected to the Ukraine pressure campaign that House impeachment investigators have not yet been informed about, his lawyer told lawmakers Friday.

The lawyer, Charles J. Cooper, made that tantalizing point in a letter to the chief House lawyer in response to House committee chairmen who have sought Bolton’s testimony in their impeachment proceedings, arguing that his client would be willing to talk but only if a court rules that he should ignore White House objections.

Cooper did not elaborate on what meetings and conversations he was referring to, leaving it to House Democrats to guess at what Bolton might know. Bolton has been one of the most anticipated witnesses because other current and former officials have described him as deeply disturbed by the effort to pressure Ukraine to provide incriminating information about Democrats to help the president’s domestic political prospects.

Bolton did not show up for a deposition scheduled Thursday because, his lawyer said, he wants a judge to determine whether he and his former deputy, Charles M. Kupperman, should testify in defiance of the White House. In effect, Bolton and Kupperman are asking for a court ruling on competing demands by the executive branch, which does not want them to testify, and the legislative branch, which does.


House Democrats complained that Bolton was stiff-arming them even though other national security officials have complied with subpoenas or requests for testimony, but the lawmakers have withdrawn a subpoena for Kupperman and indicated they would not seek one for Bolton because they said they did not want to get dragged into lengthy court proceedings. Instead, Democrats have suggested that they may cite the refusal to testify by Bolton and Kupperman as evidence of obstruction of Congress by the president, which could form its own article of impeachment.


In representing Bolton and Kupperman, Cooper denied that they were trying to delay proceedings and insisted that their legal position was not coordinated with the White House. Cooper argued that if the House were serious about an inquiry, then Bolton would be a logical person to question.

Bolton “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,” Cooper wrote in the letter.

Many witnesses who have testified so far have placed Bolton at the center of key events, describing him as exasperated by the efforts by people around the president — led by his personal lawyer Rudy Giuliani — to pressure Ukraine to investigate Democrats. Bolton said he wanted nothing to do with the “drug deal,” as he put it, that other presidential advisers were orchestrating and called Giuliani a “hand grenade who’s going to blow everybody up,” according to testimony by Fiona Hill, the president’s former top Russia and Europe adviser.

Bolton directed Hill to report to a White House lawyer her conversation with Gordon D. Sondland, the ambassador to the European Union who was involved in the pressure campaign. And he objected to Trump’s decision to suspend $391 million in security aid to Ukraine and the decision to call President Volodymyr Zelensky of Ukraine on July 25.

During that call, Trump asked Zelensky to “do us a favor” and investigate Ukrainian connections to Democrats in 2016 and former vice president Joe Biden and his son, Hunter .


Meanwhile, a transcript released Friday showed that lieutenant Colonel Alexander Vindman, the senior White House official responsible for Ukraine, said ‘‘there was no doubt’’ about what Trump wanted when he spoke by phone to Zelensky — particularly in contrast with an April call between the two shortly after Zelensky’s election.

‘‘The tone was significantly different,’’ Vindman said, according to a transcript of his Oct. 29 deposition released Friday. Vindman went on to tell Welch, ‘‘I'm struggling for the words, but it was not a positive call. It was dour. If I think about it some more, I could probably come up with some other adjectives, but it was just — the difference between the calls was apparent.’’

Material from The Washington Post was used in this report.