Cohen was speaking privately Thursday to the House intelligence committee, the last of three appearances before Congress this week.
READ: Michael Cohen's full prepared remarks for public testimony before House committee
Cohen, who pleaded guilty last year to lying to Congress and soon reports to prison for a three-year sentence, gave harsh testimony about Trump on Wednesday. He said Trump knew in advance that damaging emails about Democrat Hillary Clinton would be released, something the president has denied, and accused Trump of lying during the 2016 campaign about a Moscow real estate protect.
Cohen also said Trump directed him to arrange a hush money payment to a porn actress who said she had sex with the president a decade earlier. He said the president arranged to reimburse Cohen, and Cohen brought to the hearing a check that he said was proof of the transaction.
WATCH: Michael Cohen casts Trump as a liar, cheater, racist
Cohen's matter-of-fact testimony about secret payments and lies unfolded as Trump was thousands of miles away from Washington, meeting with North Korean leader Kim Jong Un. Trump said Thursday he tried to watch as much of Cohen's marathon congressional hearing as he could. He slammed the hearing as "fake" and said it was a "terrible thing" for Democrats to hold it during the summit.
He seized on Cohen's concession that he had no direct evidence that Trump or his aides colluded with Russia to get him elected, the primary question of special counsel Robert Mueller's investigation. Trump said he was a "little impressed" that Cohen had said that to the House Oversight and Reform Committee.
VIDEO: Michael Cohen discusses his relationship with President Trump
Cohen, shaking off incessant criticism from Republicans anxious to paint him as a felon and a liar, became the first Trump insider to pull back the curtain on a version of the inner workings of Trump's political and business operations. He likened the president to a "mobster" who demanded blind loyalty from underlings and expected them to lie on his behalf.
"My loyalty to Mr. Trump has cost me everything: my family's happiness, friendships, my law license, my company, my livelihood, my honor, my reputation and soon my freedom," Cohen said. "I will not sit back, say nothing and allow him to do the same to the country."
Michael Cohen was one of many lawyers who represented me (unfortunately). He had other clients also. He was just disbarred by the State Supreme Court for lying & fraud. He did bad things unrelated to Trump. He is lying in order to reduce his prison time. Using Crooked’s lawyer!— Donald J. Trump (@realDonaldTrump) February 27, 2019
In testimony that cut to the heart of federal investigations encircling the White House, Cohen said he arranged the hush money payment to porn actress Stormy Daniels at Trump's behest and agreed to lie about it to the public and the first lady. And he said he was left with the unmistakable impression Trump wanted him to lie to Congress about a Moscow real estate project, though the president never directly told him so.
In one revelation, Cohen said prosecutors in New York were investigating conversations Trump or his advisers had with him after his office and hotel room were raided by the FBI last April. Cohen said he could not discuss that conversation, the last contact he said he has had with the president or anyone acting on his behalf, because it remains under investigation.
The appearance marked the latest step in Cohen's evolution from legal fixer for the president - he once boasted he'd "take a bullet" for Trump - to a foe who has implicated him in federal campaign finance violations. The hearing proceeded along parallel tracks, with Democrats focusing on allegations against Trump while Republicans sought to undermine Cohen's credibility and the proceeding itself.
WATCH: Michael Cohen exposes inner workings of Trump's political, business operations
As Republicans blasted him as a convicted liar, a mostly unrattled Cohen sought to blunt the attacks by repeatedly acknowledging his own failings. He called himself a "fool," warned lawmakers of the perils of blind loyalty to a leader undeserving of it and pronounced himself ashamed of what he'd done to protect Trump.
Cohen is due to begin a three-year prison sentence in May, and he described himself as cooperative with multiple investigations in hopes of reducing his time behind bars. He is seen as a vital witness for federal prosecutors because of his proximity to the president during key episodes under investigation and their decade-long professional relationship.
The first of six Trump aides charged in the Trump-Russia investigation to testify publicly about crimes committed during the 2016 campaign and in the months that followed, Cohen also delivered biting personal commentary on a president he said never expected to win in the first place.
"The campaign - for him - was always a marketing opportunity," Cohen said.
He recounted that Trump made him threaten schools he attended to not release his grades and SAT scores and denigrated blacks as "too stupid" to vote for him. He said Trump once confided to him that, despite his public explanation of a medical deferment from the Vietnam War because of bone spurs, he never had any intention of fighting there.
"I find it ironic, President Trump, that you are in Vietnam right now," Cohen said.
Cohen gave lawmakers his first-person account of how he arranged to buy the silence of Daniels and former Playboy model Karen McDougal, who said they had sex with Trump. He described a February 2017 conversation with Trump in the Oval Office in which the president reassured him that reimbursement checks sent through Federal Express were coming but would take some time to get through the White House system.
He said the president spoke to him last year to discuss the public messaging around the transaction and even put his wife, Melania Trump, on the phone so Cohen could lie to her.
"Lying to the first lady is one of my biggest regrets," Cohen said. "She is a kind, good person. I respect her greatly, and she did not deserve that."
VIDEO: Michael Cohen reflects 'It is painful to admit that I was motivated by ambition at times'
In an allegation concerning Mueller's probe, Cohen said he overheard Trump confidant Roger Stone telling the candidate in the summer of 2016 that WikiLeaks would dump damaging information about Clinton.
Trump put Stone on speakerphone as Stone relayed that he had communicated with WikiLeaks founder Julian Assange and that "within a couple of days, there would be a massive dump of emails that would damage Hillary Clinton's campaign," Cohen said. Damaging emails U.S. officials say were hacked by Russia were later released by WikiLeaks.
Trump responded by saying "wouldn't that be great," Cohen said.
Stone disputed that account, and Barry Pollack, a lawyer for Assange, said Stone and Assange did not have the telephone call that Cohen described.
Cohen also suggested Trump implicitly told him to lie about a Moscow real estate project. Cohen has admitted lying about the project, which he says Trump knew about as Cohen was negotiating with Russia during the campaign. Cohen said Trump did not directly tell him to lie, but "he would look me in the eye and tell me there's no business in Russia and then go out and lie to the American people by saying the same thing."
Cohen said he doesn't have direct evidence that Trump colluded with the Russian government during the election but he has "suspicions," including after a June 2016 meeting between the president's oldest son and a Kremlin-connected lawyer.
"I wouldn't use the word 'colluding.' Was there something odd about the back-and-forth praise with President Putin?" Cohen said. "Yes, but I'm not really sure I can answer that question in terms of collusion."