Mr Trump has endured a week of tumult at the White House after he fired the head of the FBI, James Comey, and then discussed sensitive national security information about Islamic State with Russian Foreign Minister Sergei Lavrov.
Trump emphatically said "no" when asked during a joint news conference with Colombian President Juan Manuel Santos in the White House's East Room.
The letter was signed by both Republicans and Democrats, Charles Grassley, Dianne Feinstein, Lindsey Graham and Sheldon Whitehouse.
The White House has said that Flynn was dismissed for misleading Vice President Mike Pence about a phone call with the Russian ambassador, during which he reportedly discussed ways of softening USA sanctions on Russia. According to a report published Tuesday in New York Times, Comey's written memo of a February meeting with Trump says Trump asked Comey to back off from looking into disgraced former National Security Advisor, Michael Flynn.
Asked whether Trump's actions could be an impeachable offense, Lynch referred to the federal statue against improperly obstructing an investigation. "He is a good guy". But that explanation imploded when Trump admitted in a television interview that "when I made a decision to just do it, I said to myself, I said, "you know, this Russian Federation thing with Trump and Russian Federation is a made-up story'". "I hope you can see your way clear to letting this go, to letting Flynn go", Trump supposedly told Comey.
"You can't let them get you down".
House and Senate committees have immediately - and rightly - requested copies of the memos related to this controversy.
"Last week, the President tweeted a message implying that the White House may have recordings of interactions with Mr. Comey", wrote the ranking members of the committee, seemingly referring to Trump's May 12th tweet warning about "tapes" of conversations with Comey. That is why Congress needs to focus on establishing the truth about this matter, and soon.