Comey described the conversation with Trump in a memo he shared with other top FBI officials, according to sources who described the memo's contents to ABC News.
The story follows a Washington Post report Monday that Trump revealed classified information to Russian officials during a White House meeting last week.
In the aftermath of the news, members of Congress on both sides of the aisle called for the memo to be made available to them and for Comey to testify.
Here's what lawmakers are saying about the latest report:
RepublicansSen. Jeff Flake, R-Ariz.
Rep. Jason Chaffetz, R-Utah
Rep. Adam Kinzinger, R-Ill.
Rep. Carlos Curbelo, R-Fla.
Rep. Leonard Lance, R-N.J.
Rep. Frank LoBiondo, R-N.J.
DemocratsSenate Minority Leader Chuck Schumer, D-N.Y.
Sen. Tim Kaine, D-Va.
Sen. Tammy Duckworth, D-Ill.
Sen. Debbie Stabenow, D-Mich.
Sen. Richard Blumenthal, D-Conn.
Sen. Brian Schatz, D-Hawaii
Sen. Mazie Hirono, D-Hawaii
House Minority Leader Nancy Pelosi, D-Calif.
"If these reports are true, the president's brazen attempt to shut down the FBI's investigation of Michael Flynn is an assault on the rule of law that is fundamental to our democracy. At best, President Trump has committed a grave abuse of executive power. At worst, he has obstructed justice.
"With each passing day, the president's actions give greater and greater urgency to the need for a full and independent investigation of the Trump-Russia connection. Tomorrow, Democrats will file a discharge petition to demand a vote on the bipartisan bill to establish an independent, outside commission to investigate Trump's ties to Russia. Soon, Democrats will also introduce legislation to create an independent counsel to get the facts free of President Trump's meddling.
"If the president has nothing to hide, then he should welcome independent investigations to remove all doubt of a cover-up. The American people deserve to know what President Trump is so desperate to keep hidden."