Congressional investigators have rebuffed former US national security adviser Michael Flynn's offer of cooperation in exchange for immunity from prosecution.
Members of the Senate intelligence committee decided it is too early in their probe of Russia connections to discuss a deal.
President Donald Trump tweeted that Mr Flynn, his former adviser, should ask for immunity because he is facing "a witch hunt".
Mr Flynn's attorney said talks have taken place about immunity in order for him to testify. Intelligence committees in both the Senate and House are investigating Russia's meddling in the 2016 presidential election.
A congressional aide confirmed that preliminary discussions with the Senate intelligence committee involved immunity but that it was too early in the investigation to set terms.
Mr Trump weighed in on Friday, tweeting that Flynn "should ask for immunity in that this is a witch hunt (excuse for big election loss), by media & Dems, of historic proportion!"
It was unclear from that tweet whether he was advising the Justice Department or the congressional panels to give his former adviser immunity. The president is not supposed to direct ongoing investigations.
White House spokesman Sean Spicer said Mr Trump just wants Mr Flynn to testify, and there are no concerns that he could implicate the president in any wrongdoing.
The top Democrat on the House intelligence committee, Adam Schiff, of California, said committee leaders would be discussing the issue with their Senate counterparts and the Justice Department.
"We should first acknowledge what a grave and momentous step it is for a former national security adviser to the president of the United States to ask for immunity from prosecution," Mr Schiff said.
Mr Flynn's attorney Robert Kelner said no "reasonable person" who has a lawyer would answer questions without assurances that he would not be prosecuted, given calls from some members of Congress that the retired lieutenant general should face criminal charges.
"General Flynn certainly has a story to tell, and he very much wants to tell it, should the circumstances permit," Mr Kelner said on Thursday.
Mr Spicer said the president wants Mr Flynn to testify in front of the committees.
"He thinks he should go out and tell his story," Mr Spicer said on Friday.
Mr Flynn's ties to Russia have been scrutinised by the FBI and are under investigation by the congressional committees.
Both panels are looking into Russia's meddling in the election and any ties between Trump associates and the Kremlin.
Since July, the FBI has been conducting a counter-intelligence investigation into Russia's interference in the election and possible coordination with Trump associates.
In September, Mr Flynn weighed in on the implications of immunity on NBC's Meet The Press, criticising Democratic presidential candidate Hillary Clinton and her associates in the FBI's investigation into her use of a private email server.
"When you are given immunity, that means that you have probably committed a crime," Mr Flynn said during the interview.
A spokesman for Devin Nunes, the Republican chairman of the House intelligence committee, said the panel has not offered an immunity deal to Mr Flynn.
The committee "had a preliminary conversation with Michael Flynn's lawyer about arranging for Flynn to speak to the committee," spokesman Jack Langer said. "The discussions did not include immunity or other possible conditions for his appearance."