A lawyer for a whistleblower who triggered the impeachment inquiry into President Donald Trump has sent a cease and desist letter to the White House.
In the letter, Andrew Bakaj writes that Mr Trump’s “rhetoric and activity” places his client and family “in physical danger”.
Since the whistleblower report was released, Mr Trump has continuously attacked the unnamed official.
The official’s identity has so far been fiercely guarded by Democrats.
The individual filed a whistleblower report in August expressing concern over a call a month earlier between Mr Trump and his Ukrainian counterpart Volodymyr Zelensky.
Mr Trump asked Mr Zelensky to investigate Joe Biden, now a Democratic front-runner for the White House election next year. The call occurred shortly after Mr Trump had withheld US military aid to Ukraine.
In the letter, sent to White House counsel Pat Cipollone on Thursday, Mr Bakaj cites multiple examples of the president’s “fixation” on the identity of the whistleblower in his comments to the media, at rallies and on Twitter.
“Such statements seek to intimidate my client – and they have,” Mr Bakaj writes.
He continued: “Let me be clear: should any harm befall any suspected named whistleblower or their family, the blame will rest squarely with your client.”
The president’s daughter, Ivanka Trump, has meanwhile said she did not believe the whistleblower’s identity was “particularly relevant”.
“The whistleblower shouldn’t be a substantive part of the conversation,” she told the Associated Press, adding that the person “did not have firsthand information”.
She echoed her father’s view that the impeachment investigation is about “overturning the results of the 2016 election”.
Democrats have said the whistleblower’s identity is irrelevant since they argue that the complaint, which alleges abuse of power by Mr Trump, has been substantiated by witness testimony to the impeachment committees.
The Democratic-controlled House of Representatives will next week hold televised impeachment hearings for the first time in this inquiry.
If the House eventually votes to impeach Mr Trump, the Republican-controlled Senate will hold a trial of the president.
If Mr Trump is convicted – widely viewed at present as unlikely – he would be removed from office.
But Senator Josh Hawley, a Republican, said on Thursday he wants to know the identity of the whistleblower if there is an impeachment trial in the upper chamber.
He also said the president’s team should be able to question the anonymous official.
“I can’t control what goes on in the House, but if it comes over to the Senate and we have a trial I’m going to want to know who the whistleblower is,” Mr Hawley told Missouri radio station KFTK.
“How else are we going to evaluate the content and the truthfulness of these people if we don’t know who they are?”