Lawyer of the US president Rudy Giuliani looks on before the US president announces his Supreme Court nominee in the East Room of the White House on July 9, 2018 in Washington, DC.

Rudy Giuliani on Tuesday defied a subpoena from House committees that are conducting an impeachment probe of his legal client, President Donald Trump.

Tuesday was the deadline for Giuliani, who is Trump's personal lawyer, to turn over to the committees documents related to Ukraine.

"Mr. Giuliani will not participate because this appears to be an unconstitutional, baseless, and illegitimate 'impeachment inquiry,' " Giuliani's lawyer, Jon Sale, wrote in a letter to the House.

Sale's letter called the subpoena "overbroad, unduly burdensome, and seeks documents beyond the scope of legitimate inquiry."

"Moreover, documents sought in the subpoena are protected by attorney-client, attorney work-product, and executive privilege," the letter said.

Giuliani had pushed the government of Ukraine to investigate former Vice President Joe Biden in connection with what Giuliani has claimed was improper past pressure by Biden on Ukraine to dismiss a prosecutor in that country. Trump and Giuliani have suggested, without evidence, that Biden was acting to protect his son, Hunter Biden, who was serving on the board of a Ukrainian natural gas company.

That push has put Trump at risk of impeachment after the president supported Giulani's effort by himself asking Ukraine's president in July to investigate Biden, even as Trump withheld congressionally appropriated military aid from Ukraine.

Congressional Democrats launched an impeachment inquiry after learning Trump may have used his office to get a foreign country to investigate Biden, who is seeking the 2020 Democratic presidential nomination.

"Your failure or refusal to comply with the subpoena, including at the direction or behest of the President or the White House, shall constitute evidence of obstruction of the House's impeachment inquiry and may be used as an adverse inference against you and the President," the committees said in a letter to Giuliani last month notifying him of the demand for the Ukraine documents.

The subpoena was issued by the House Intelligence, Oversight, and Foreign Affairs committees.

"Witnesses do not get to choose whether to comply with a duly-authorized subpoena, or to pick their investigators — not in the justice system, not in the Congress, and not in our democracy," an official working on the impeachment probe told NBC News. "If Rudy Giuliani and the President truly have nothing to hide about their actions, Giuliani will comply — otherwise, we will be forced to consider this as additional evidence of obstruction, and may infer that the evidence withheld would substantiate the accusations of President Trump's misconduct and efforts to cover it up."

Sale, a former assistant special prosecutor in the Watergate case, is no longer representing Giuliani. According to Sale, he was only retained by Giuliani to handle the subpoena inquiry.

Giuliani did not immediately return a request for comment from CNBC.

But he did tweet Sale's letter, and wrote, "I will not participate in an illegitimate, unconstitutional, and baseless 'impeachment inquiry.' "

Tweet

Former White House official Fiona Hill reportedly told Congress in a closed-door deposition on Monday that then-national security advisor John Bolton was so worried about the pressure on Ukraine by Giuliani and others that he told Hill to alert the chief lawyer for the National Security Council.

Bolton euphemistically called that effort a "drug deal," The New York Times reported, citing sources familiar with Hill's testimony.

And Bolton reportedly called Giuliani a "hand grenade."

Giuliani said, "I always liked and respected John" Bolton, according to NBC News.

""I'm very disappointed that his bitterness drives him to attack a friend falsely and in a very personal way. It's really ironic that John Bolton is calling anyone else a hand grenade," Giuliani said. "When John is described by many as an atomic bomb."