The US official whose whistleblower complaint led to the impeachment inquiry against President Donald Trump offered to communicate directly with Republicans on the intelligence committee leading the inquiry, his lawyers said on Sunday.
The action was in response to Republican efforts, led by Trump, to unmask the whistleblower, a member of the US intelligence community whose identity has not been released, lawyer Mark Zaid said. Republicans have "sought to expose our client's identity which could jeopardise their safety, as well as that of their family," Zaid wrote on Twitter.
News of the offer came as Trump called on the whistleblower to come forward, in a stark departure from norms in such cases.
"The Whistleblower got it so wrong that HE must come forward," Trump said in a morning Twitter post.
Later outside the White House, Trump called the whistleblower an "Obama guy" and a fraud and said, "The whistleblower should be revealed."
Republicans have complained the impeachment inquiry in the Democratic-led House of Representatives has been unfair to them and to Trump, and that they have been restricted in their questioning of witnesses. The inquiry has followed established House rules.
The Republican president is under increasing pressure as the House of Representatives forges ahead with its investigation of whether Trump solicited help from Ukraine as he seeks re-election next year. Leaders of the Democratic-controlled House expect to begin public hearings in the next few weeks.
The inquiry was launched on September 24 after a whistleblower complaint from the unidentified US intelligence official who was concerned the president's actions on Ukraine were illegal and jeopardized national security.
As the inquiry enters its sixth week, however, the whistleblower's testimony, based on second-hand information provided by other US officials, is not likely to be the most important.
Lawmakers leading the inquiry have since heard first-hand accounts from US officials including former National Security Council member Alexander Vindman that describe Trump's efforts to pressure Ukraine to investigate the 2020 Democratic candidate Joe Biden and his son Hunter, as well as accusations he used $391 million in US aid as leverage.
A White House summary of a phone call between Trump and Ukraine President Volodymyr Zelenskiy showed Trump asking his Ukrainian counterpart to investigate the Bidens.
Democrat Adam Schiff, the House Intelligence Committee chairman, said last month the whistleblower's testimony might not be necessary.
The whistleblower initially offered to answer questions in writing if submitted by the House Intelligence Committee as a whole.
Zaid said the new offer, made on Saturday to top intelligence panel Republican Devin Nunes, reflected the client's desire to have the complaint handled in a nonpartisan way.
"Let me be absolutely clear: Our willingness to cooperate has not changed. What we object to and find offensive, however, is the effort to uncover the identity of the whistleblower," added Andrew Bakaj, another of the whistleblower's lawyers.
Nunes' office did not return a request for comment.
Longstanding Intelligence Committee policy is to protect whistleblowers' anonymity.
Trump has repeatedly lashed out at the whistleblower and called for his identity to be made public. He denies any impropriety and says the impeachment is politically motivated.
"They have the right to remain anonymous," Schiff said after Vindman's deposition last week.
Trump on Sunday said Schiff cannot be trusted to release accurate transcripts of testimony given by witnesses in the impeachment inquiry. Trump on Twitter called the congressman "a proven liar, leaker & freak who is really the one who should be impeached!"
Trump said Republican lawmakers should "give their own transcripts of the interviews to contrast with Schiff's manipulated propaganda."