WASHINGTON — An American lobbyist on Friday admitted brokering access to President Trump’s inauguration for a pro-Russian Ukrainian oligarch in a scheme that highlighted the rush by foreign interests to influence the new administration.
As part of a plea agreement under which he pledged to cooperate with federal prosecutors, the lobbyist, Sam Patten, pleaded guilty to failing to register as a foreign agent for a Russia-aligned Ukrainian political party, and to helping the Ukrainian oligarch who had funded that party illegally purchase four tickets to Mr. Trump’s inauguration.
Although the charges were not brought by the special counsel investigating Russian interference in the 2016 presidential election, Robert S. Mueller III, they stem from his team’s work, and overlap substantially with its continuing investigation, suggesting that Mr. Patten could be a useful witness.
The case sketched out by prosecutors encompassed Mr. Patten, a respected Republican operative and consultant whose family was once part of Washington’s social elite; money transfers from a Cypriot bank; and a Russian national who had also worked for Paul Manafort, Mr. Trump’s former campaign manager, and been accused of maintaining ties to Russian intelligence.
The charges against Mr. Patten also represented the first public acknowledgment that prosecutors are looking into efforts by foreign interests to funnel money into Mr. Trump’s political operation, including his inaugural committee.
Prosecutors did not present any evidence that the inaugural committee was aware of the scheme. Questions to representatives of the inaugural committee on Friday about the illegal purchase of tickets went unanswered.
Mr. Trump’s inauguration came at a moment when some international figures were paying large sums to Mr. Trump’s associates in an effort to curry favor with an administration that came into office with few ties to established players on the world stage, and with an uncertain foreign policy agenda. That was particularly true in matters related to Russia and its neighbors.
During his campaign, Mr. Trump flouted traditional foreign policy by praising President Vladimir V. Putin of Russia and suggesting that if elected he might be willing to ease sanctions levied against Russia over its aggression against Ukraine.
That alarmed allies of Petro O. Poroshenko, the Ukrainian president, who is generally regarded as more pro-Western, and it emboldened his pro-Russian opponents, who had held power from 2010 to 2014 partly through the efforts of Mr. Manafort and his former right-hand man, Rick Gates.
Forced into the opposition, the oligarchs formed a political party called Opposition Bloc, which worked with Mr. Manafort and Mr. Gates in 2014, before largely shifting its political consulting and lobbying business to a company started by Mr. Patten and Konstantin V. Kilimnik. He is a Russian national who had worked closely with Mr. Manafort in Ukraine and is suspected by the United States of having ties to Russian intelligence.
The company was paid more than $1 million through an offshore Cypriot bank account to advise the party and its members, including a “prominent Ukraine oligarch” between 2014 and this year, according to a court document filed on Friday.
Prosecutors contend that Mr. Patten should have disclosed the work, which included lobbying and public relations assistance intended to “influence United States policy,” with the Justice Department pursuant to the Foreign Agents Registration Act.
Mr. Patten also attended an unspecified inaugural event with the oligarch, according to prosecutors. They contend that Mr. Patten arranged for the purchase of four tickets for $50,000 by funneling the oligarch’s money through an American “straw” purchaser in violation of rules barring the inaugural committee from accepting money from foreign nationals.
Mr. Patten intentionally withheld documents from the Senate Intelligence Committee that could have revealed that foreign money was used to purchase the tickets, according to court filings.
Mr. Patten’s lawyer declined to comment after a Friday court hearing in which Mr. Patten entered his guilty plea. He faces up to five years in prison and a fine of up to $250,000. He was released after the hearing and awaits sentencing.
Prosecutors did not identify the American who purchased the tickets, the oligarch or Mr. Patten’s Russian business partner by name.
But people familiar with the work said the Russian is Mr. Kilimnik, who formed a company called Begemot Ventures International with Mr. Patten in February 2015, according to corporate records filed in Washington.
And the description of the oligarch matches that of Serhiy Lyovochkin, who serves in the Ukrainian parliament and is an official in the Opposition Bloc, according to interviews and documents. Prosecutors say that Mr. Patten arranged meetings with congressional officials for the oligarch, and one former congressional aide recalled being introduced to Mr. Lyovochkin by Mr. Patten.
Prosecutors also said that Mr. Patten helped the oligarch draft and place an op-ed in an American media outlet in February 2017 “to address concerns regarding Ukraine’s ability to work effectively with the new United States administration.”
An op-ed under Mr. Lyovochkin’s name appeared in U.S. News & World Report at that time arguing that Mr. Trump could be good for Ukraine, while accusing elements of Mr. Poroshenko’s government of trying to boost Hillary Clinton, including by “manufacturing” allegations against Mr. Manafort related to his work for the ousted pro-Russian president, Viktor F. Yanukovych.
A representative of U.S. News said editors had not been contacted by anyone in law enforcement about the op-ed.
Mr. Lyovochkin surfaced prominently in the financial fraud trial last month of Mr. Manafort. Mr. Gates, Mr. Trump’s former deputy campaign chairman and Mr. Manafort’s former right-hand man, testified that Mr. Lyovochkin was one of a clutch of oligarchs who paid Mr. Manafort more than $60 million to promote pro-Russian political forces in Ukraine.
With Mr. Manafort’s help, Mr. Yanukovych was elected president of Ukraine in 2010, a position he held for four years until he fled to Russia amid a popular uprising against his regime’s corruption.
Mr. Gates testified that Mr. Lyovochkin wired millions of dollars to Mr. Manafort’s secret bank accounts from bank accounts in Cyprus held in the names of two shell companies to Mr. Manafort’s secret bank accounts. Like the other Ukrainian oligarchs who financed Mr. Manafort’s work, Mr. Lyovochkin was one of the top officials in Mr. Yanukovych’s government.
After Mr. Yanukovych was forced out of office, the oligarchs regrouped into an opposition force, continuing to pay Mr. Manafort for a time to help promote their views in the West.
Mr. Manafort was convicted in August of financial fraud and is scheduled to go on trial in September on other charges, including violating the Foreign Agents Registration Act for failing to disclose his work on behalf of Mr. Yanukovych and the Opposition Bloc.
Mr. Patten traveled in the same lucrative foreign consulting circles as Mr. Manafort, but people who know them said their primary connection was through Mr. Kilimnik.
Mr. Patten was born into elite Washington, as a grandson of the Georgetown socialite Susan Mary Alsop.
He worked in Washington Republican politics, including for the State Department under President George W. Bush, and briefly for Senator Susan Collins of Maine.
But Mr. Patten really made his name in international political consulting, coming to specialize in representing clients in former Soviet states. He worked with Mr. Kilimnik in the Moscow office of the International Republican Institute in the early 2000s.
In Ukraine, Mr. Patten and Mr. Kilimnik worked on the 2014 campaign of the former boxer Vitali Klitschko for mayor of Kiev, which was also supported by Mr. Lyovochkin.
And Mr. Patten also worked extensively for interests in Kazakhstan.
Among his associates on work related to Kazakhstan was Rinat Akhmetshin, a Russian-born Washington lobbyist who attended the June 2016 Trump Tower meeting at which Kremlin-linked insiders had promised to provide the Trump campaign with damaging information about Mrs. Clinton.
Mr. Patten also had a yearslong business relationship with Cambridge Analytica, the political data firm that worked on Mr. Trump’s 2016 campaign. Starting in 2014, the firm used Mr. Patten as a consultant for election campaigns and other projects in Africa, Europe and the United States, according to a person with direct knowledge of his activities.
During the same year, Cambridge Analytica sought to drum up business in Russia, approaching the Russian oil giant Lukoil.
In a Facebook post, Mr. Patten said he deeply regretted his failure to register as a foreign agent and was “ashamed” that he had undermined much of his life’s work, which he said had largely focused on promoting democracy abroad.
Eileen Sullivan and Nicholas Confessore contributed reporting.