Trump whistleblower's lawyers have 'serious concerns' for client's personal safety The lawyers cite President Trump's attacks as one reason for their concern.

The legal team representing the whistleblower whose claims sparked the impeachment inquiry and President Donald Trump's ire is expressing “serious concerns” for their client’s personal safety, according to a letter sent to acting Director of National Intelligence Joseph Maguire.

Andrew Bakaj, an attorney for the whistleblower, writes that “the events of the past week have heightened our concerns that our client’s identity will be disclosed publicly and that, as a result, our client will be put in harm’s way.” Bakaj also claimed that “certain individuals have issued a $50,000 “bounty” for “any information” relating to our client’s identity.”

The legal team declined comment on the specific security issues raised.

"The current environment is one that requires sensitivity and intelligence about security and there are ongoing discussions about how to best to prepare for worst-case scenarios," a source close to the case told ABC News.

In the letter to Maguire, Bakaj cited President Trump’s comments about the whistleblower’s sources as cause for concern. In a closed door meeting last Thursday, a video recording shows Trump saying telling an audience “I want to know who’s the person that gave the whistleblower, who’s the person that gave the whistleblower the information, because that’s close to a spy. You know what we used to do in the old days when we were smart? Right? With spies and treason, right? We used to handle them a little differently than we do now.”

Although the president’s comments were directed at the person or persons who shared information with the whistleblower, Bakaj said it “does nothing to assuage our concerns for our client’s safety.”

The whistleblower’s legal team also forwarded their letter to Maguire to the leadership of the House and Senate intelligence committees, calling on both parties to call out for whistleblower protection and “reiterate that this is a protected system where retaliation is not permitted, whether direct or implied.”

In Bakaj’s letter to Maguire, he states “we expect this situation to worsen, and to become even more dangerous for our client and any other whistleblowers, as Congress seeks to investigate this matter.”

In a tweet sent Monday afternoon, Bakaj said, "The Intel Community Whistleblower is entitled to anonymity. Law and policy support this and the individual is not to be retaliated against. Doing so is a violation of federal law."

Sen. Mark Warner, the top Democrat on the Senate Intelligence Committee, told ABC News on Monday, “I think it would be reasonable, if this person were to come forward, that he or she probably deserves some protection, protective services for a while because of the jeopardy by the president's, I think, irresponsible comments has potentially put this person in.”

Over the weekend, House Intelligence Chairman Adam Schiff, D-Calif., told ABC Chief Anchor George Stephanopoulos on “This Week” Sunday that an agreement had been reached with Maguire to allow the whistleblower to appear before his committee. “We'll get the unfiltered testimony of that whistleblower,” Schiff said, adding that the committee is “taking all the precautions” possible to protect the whistleblower's identity.

The president, who has denied any wrongdoing alleged in the whistleblower’s complaint focusing on a July phone call between Trump and the president of the Ukraine, tweeted Sunday “I deserve to meet my accuser, especially when this accuser, the so-called “Whistleblower,” represented a perfect conversation with a foreign leader in a totally inaccurate and fraudulent way.” Trump also doubled down on his threats directed at the whistleblower’s sources, saying they would face “big consequences.”

The intelligence community’s inspector general found that the whistleblower’s complaint was “credible” and of “urgent concern.” That complaint was released to the public last Thursday, ahead of acting Maguire’s testimony before the House Intelligence Committee on his handling of the complaint.

Trump’s allies have attempted to discredit the whistleblower’s credibility. Mark Levin, a radio host and Trump supporter, appeared on “Fox and Friends” on Saturday to demand more information on the whistleblower, saying “I want to know everything about him! I want to know what kind of dogs they have, how many marriages they've had, if they have a DUI, if they're a partisan, I want to know everything!”

Although the House and Senate are on a two-week break, members of the House involved in the impeachment inquiry are working through the recess, with depositions related to the probe scheduled to begin this week.

The whistleblower’s legal team said in a statement that they were continuing to work “with both parties in the House and Senate and we understand and agree that protecting the whistleblower’s identity is paramount.”

A time or date has yet to be set for the hearing, which will likely occur behind closed doors to protect the whistleblower’s anonymity. When asked about projected timing for the testimony, Schiff said he expected to hear from the whistleblower “very soon.”

ABC News' James Gordon Meek contributed to this report.