Update | The former personal attorney and self-proclaimed "fixer" for President Donald Trump reportedly received a payment of at least $400,000 to set up a meeting between Trump and Ukraine's president previous year.
Federal prosecutors in NY are investigating Mr Cohen for possible bank and tax fraud, campaign law violations and perhaps other matters related to Mr Trump's presidential campaign, a source said.
Cohen is under criminal investigation by federal prosecutors in NY for his business dealings, as well as for a $130,000 hush-money payment he made to porn star Stormy Daniels right before the 2016 presidential election. Friedman was facing what would have amounted to a life sentence, the source said, but if he satisfies the terms of the agreement, he will receive just five years of probation.
The plea by Freidman, a taxi operator who was charged with failing to pay US$5 million (S$6.7 million) in taxes, could provide the government with a new source of information about Mr Cohen.
Public records show that Cohen took out a business loan in late 2014 for an unspecified amount using three taxi companies as collateral.
"Gene Friedman and I are not partners and have never been partners in this business or any other", Cohen tweeted on Wednesday.
Before Cohen's intervention, Ukrainian representatives were only able to get a brief photo op for the Ukrainian president - who has been openly critical of Russian President Vladimir Putin - with Mr. Trump.
The claims line up with those of porn star Stormy Daniels" lawyer Michael Avenatti, who said Suspicious Activity Reports filed by Cohen's bank to US Treasury officials revealed payments from "Ukrainian interests'. I am humbled and shamed. This is me taking responsibility for my actions. "This is a very hard day for myself and my family".
A Ukrainian official said Mr. Cohen was paid US$400,000, while another source put the figure at US$600,000, the BBC reported.
Freidman pleaded guilty in Albany to one count of evading $50,000 worth of taxes.
But that same Port Washington channel may have been used before in an effort by affiliates of Russian President Vladimir Putin to end sanctions against Moscow over its invasion of Ukraine, according to reports in The New York Times.
Mr Cohen is facing a probe by the United States attorney's office in Manhattan, which is examining his business practices.
"I can not comment on any speculation regarding what the entry of the plea indicates regarding any case other than my client's", he said.