A lawyer for the whistleblower whose complaint prompted the impeachment inquiry into President Donald Trump has sent a cease-and-desist letter to the White House urging the president to stop attacking his client.

“I am writing out of deep concern that your client, the president of the United States, is engaging in rhetoric and activity that places my client, the intelligence community whistleblower, and their family in physical danger,” the lawyer, Andrew Bakaj, wrote in a letter to White House counsel Pat Cipollone on Thursday.

“I am writing to respectfully request that you counsel your client on the legal and ethical peril in which he is placing himself should anyone be physically harmed as a result of his, or his surrogates’, behavior,” he wrote.

In recent weeks, Trump has escalated his attacks on the whistleblower, whose anonymity is afforded limited protection under federal law. On Sunday, Trump told reporters, "The whistleblower should be revealed” because, the president claimed, the person "gave false information." Last month, Trump tweeted that the whistleblower "must testify" before Congress, adding, "We must determine the Whistleblower's identity to determine WHY this was done to the USA."

In the letter, Bakaj cited three other examples of Trump's attacks on the whistleblower. In one instance, Trump made a veiled reference to execution when he told a private group in September that the people who gave information to the whistleblower were "close to a spy" and said the U.S. should "handle" them like it did "in the old days."

"In the 'old days,' spies were summarily executed," Bakaj noted in his letter, adding that Trump encouraged the press to report the whistleblower’s name and tweeted the comments of a supportive pastor who told Fox News in September that impeaching the president would lead to a "Civil War-like fracture in this nation."

“His calls to the public to identify my client by name and his suggestion that he would support acts of violence against my client are, candidly, some of the most dangerous and reckless things a president of the United States can say,” Bakaj said.

Donald Trump Jr., the president's eldest son, on Wednesday tweeted the name of a person who some conservative media outlets have alleged is the intelligence community whistleblower. Trump Jr. said in a follow-up tweet that he did not coordinate his post with the White House.

For safety concerns, NBC News is not reporting the name of the whistleblower as long as the person remains anonymous. In the complaint, the whistleblower alleges that in a July 25 phone call, Trump asked Ukrainian President Volodymyr Zelenskiy to investigate former Vice President Joe Biden and his son Hunter, who had business dealings in the country, as well as a 2016 election conspiracy theory.

In his letter, Bakaj alleged that Trump's attacks constituted witness tampering and had succeeded in intimidating his client, which the lawyer alleged was their aim. The whistleblower had been in talks to give a closed-door deposition to the House Intelligence Committee, Bakaj said, but "as a direct consequence of the president’s irresponsible rhetoric and behavior, my client’s physical safety became a significant concern, prompting us to instead state our willingness to only answer written interrogatories."

Bakaj also warned the White House counsel about any actions that would violate two other federal statutes involving obstruction and retaliation.

“Let me be clear: Should any harm befall any suspected named whistleblower or their family, the blame will rest squarely with your client,” he wrote.

"I submit that it is in your client’s best interest to cease and desist in calling for the public disclosure of my client’s identity and to cease in rhetoric that may endanger their life and the lives of their family," Bakaj continued. "Should anyone be physically harmed, my co-counsel, Mark Zaid, and I will not hesitate to take any and all appropriate action against your client."