Richard Burr, the Republican chairman of the Senate intelligence committee, will step down while an insider trading inquiry is carried out.
He said he had decided to do so because he did not want the investigation to distract the committee from its work.
Senator Richard Burr’s phone has been seized by the FBI as part of the inquiry.
The 64-year-old North Carolina senator, who denies wrongdoing, allegedly used inside information to avoid market losses from coronavirus.
He declined a request for comment.
Richard Burr and his wife sold as much as $1.7 million of equities in February, just before markets plunged on fears of an economic crisis.
It is illegal for members of Congress to trade based on non-public information gathered during their official duties.
Republican Senators Kelly Loeffler of Georgia and James Inhofe of Oklahoma, as well as Democratic Senator Dianne Feinstein of California, also reportedly sold holdings before the downturn, but are not confirmed to be under investigation.
Dianne Feinstein said she had answered questions from the FBI regarding trades made by her husband, however.
Republican Senate Majority Leader Mitch McConnell said Senator Burr had contacted him to inform of his decision to step aside temporarily.
“We agreed that this decision would be in the best interests of the committee and will be effective at the end of the day tomorrow [May 15],” Mitch McConnell said in a statement.
Richard Burr said: “The work the Intelligence Committee and its members do is too important to risk hindering in any way. I believe this step is necessary to allow the Committee to continue its essential work free of external distractions.”
The senator turned over his mobile phone to authorities after federal agents issued and executed a search warrant at his Washington, DC, home.
The justice department began investigating Richard Burr in March.
Public disclosures first investigated by ProPublica show the senator sold more than 30 stocks between late January and mid-February. Some of the stocks were in sectors now devastated by the coronavirus outbreak, such as the hotel, restaurant and shipping industries.
As chairman of the Senate intelligence committee, Richard Burr receives nearly daily briefings on threats to US national security. He defended the transactions, saying he had “relied solely on public news reports” to instruct his decision to sell.
However, the senator was criticized for publicly downplaying the seriousness of the virus, even as he privately sold equities and warned a private North Carolina business group of the stark risks it posed.
Richard Burr’s lawyer, Alice Fisher, said in March the senator welcomed the justice department investigation because it would “establish that his actions were appropriate”.
“The law is clear that any American – including a Senator – may participate in the stock market based on public information, as Senator Burr did,” she said.
The bulk of Richard Burr’s sales occurred on February 13, just before his speech to the wealthy business constituent group about the dire economic impact of the coronavirus, at a time when the Trump administration was publicly downplaying the threat.
In an audio recording, obtained by US outlet National Public Radio (NPR) Richard Burr also told the group to curtail their travel. He has accused NPR of “misrepresenting” his speech.
First elected to the Senate in 2004, Richard Burr chaired the Senate Intelligence Committee when it investigated Russian election interference in the 2016 presidential election.
The committee endorsed intelligence community findings that Russia had interfered on President Donald Trump’s behalf.
Richard Burr’s six-year term ends in 2023 and he does not plan to run for re-election, the Associated Press reports.