Patten pleaded guilty before U.S. District Court Judge Amy Berman Jackson, who will also be hearing a case against Manafort starting September 24 involving charges of money laundering and failing to file as a foreign agent.
The charges are spelled out in a criminal information, which often precedes a guilty plea.
Patten was a business associate of Konstantin Kilimnik, a man US authorities say has ties to Russian intelligence.
Kilimnik is charged alongside Manafort in a separate criminal case brought in Washington by Mueller.
Friday's charging documents state that Patten worked with an unnamed Russian to place op-ed articles in USA media in 2017 and was paid more than $1 million for the Ukrainian opposition bloc work, including meeting with members of the executive branch, Senate Foreign Relations Committee members and other members of Congress.
As part of his lobbying work, he violated the Foreign Agents Registration Act, the USA said.
The funds were allegedly paid via an offshore account in Cyprus from a "prominent Ukraine oligarch" who is an Opposition Bloc member.
Begemot, which is Russian for "behemoth", matches details of the unidentified firm that prosecutors say received cash for Patten's Ukraine work.More news: Cardiff 2-3 Arsenal: Five Things We Learned
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Watching from the gallery was Andrew Weissmann, an expert on money laundering and complex fraud cases who will be the lead prosecutor in Manafort's trial in Washington.
Patten appeared in federal court in Washington on Friday.
Patten surrendered his passport and was released on his own recognizance pending sentencing. To avoid rules banning the foreign donations, Patten redirected the funds through a straw donor.
Lyovochkin's name also came up during Manafort's trial earlier this month. The charge is a felony that is punishable by a statutory maximum of up to five years in prison, and potential financial penalties. Prosecutors say that Patten arranged the purchase of four tickets for the unnamed Ukrainian oligarch to Trump's inauguration.
Patten and Konstantin Kilimnik, another Manafort associate, launched what is believed to be "Company A" in 2015.
In an 2017 interview with The Washington Post, Patten said he met Kilimnik in Moscow more than 15 years ago, when Kilimnik was an employee of the International Republican Institute, a pro-democracy group affiliated with the Republican Party. Back in June, Mueller issued a superseding indictment, adding obstruction of justice and conspiracy charges to a litany of lobbying and fraud offenses allegedly committed by Manafort.
Patten violated FARA by contacting members of Congress, the executive branch, and the media without disclosing that work to the Justice Department, according to the documents.
Even though Trump and his legal team have indicated that they would wait until after special counsel Robert Mueller's investigation wraps up, the pardoning of Paul Manafort reportedly is, and will continue to be on the table.