On Thursday, Cohen made a surprise appearance in a New York court at around 9am local time (14G) and began entering the plea.
He admitted to making false statements in 2017 to the US Senate Select Committee on Intelligence about a plan to build a Trump Tower in Moscow.
Cohen said he made the misstatements to be consistent with Trump’s political messaging and out of loyalty to his former client.
In August, Cohen had pleaded guilty to other federal charges involving his taxi businesses, bank fraud and his campaign work for Trump.
Federal prosecutors in New York began investigating Cohen after a referral from US Special Counsel Robert Mueller, who has been investigating Russian meddling in the 2016 election and possible coordination with the Trump campaign.
Thursday’s guilty plea may signal Cohen is hoping for a lighter sentence on the charges in exchange for continuing to cooperate with Mueller’s Russia investigation.
Among other lies, Cohen said on Thursday he told Congress that all discussions of the Moscow Trump Tower project ended by January 2016, when they had actually continued until June of that year.
Cohen also said that in the statement to Congress, he claimed to have had limited contact with Trump concerning the project, when in fact it had been “more extensive”.
Cohen added that he falsely told Congress he never took any steps towards travelling to Russia, when in fact he had discussed travelling there, although he never did.
Cohen’s lawyer Guy Petrillo said his client continues to cooperate with Mueller’s investigation into Russian election interference and possible coordination with Trump associates.
One of the prosecutors working with Mueller was present in the court on Thursday.
Trump, meanwhile, denied working on the Moscow real estate project and called Cohen a “weak person” who is “lying” to get a reduced sentence.
“He is a weak person. And what he is trying to do is get a reduced sentence. So he is lying about a project that everybody knew about,” Trump told reporters at the White House on Thursday.
Reacting to the plea to the new charges, House Speaker Paul Ryan said Cohen “should be prosecuted to the extent of the law. That’s why we put people under oath.”
Cohen gave a statement to congressional committees last year saying the president’s company pursued a project in Moscow during the Republican primary but that the plan was abandoned “for a variety of business reasons”.
Cohen also said he sent an email to the spokesman for Russian President Vladimir Putin as part of the potential deal.
He had also disclosed that Trump was personally aware of the deal, signing a letter of intent and discussing it with him on two other occasions.