Washington (CNN) Washington lobbyist W. Samuel Patten pleaded guilty Friday to acting as an unregistered foreign lobbyist, and admitted to lying to the Senate Intelligence Committee and funneling a Ukrainian oligarch's money to Donald Trump's Presidential Inaugural Committee.

Patten's plea and cooperation agreement is connected to special counsel Robert Mueller's ongoing investigation into Russian interference in the election and coordination with the Trump campaign -- even apparently reaching into former Trump campaign chairman Paul Manafort's inner circle in Ukraine.

This is the first time the Justice Department has publicly charged a person for helping a foreigner secretly funnel money into a Trump political event. Under his deal with prosecutors, Patten is charged only with one criminal count. He faces a maximum of five years in prison and a $250,000 fine for the felony charge. A sentencing date has not been set.

Patten sought tickets to Trump's inauguration on behalf of an unnamed prominent Ukrainian oligarch, according to court documents released Friday, ultimately paying $50,000 for four tickets. Patten used another American as a "straw purchaser," funneling the Ukrainian's money secretly to the inaugural committee through a Cypriot bank account.

"Patten was aware at the time that the Presidential Inauguration Committee could not accept money from foreign nationals," prosecutors wrote in the filing.

Rudy Giuliani, the President's lawyer, told reporters Friday Patten's case had nothing to do with his client.

"It turned about to be this irrelevant indictment, where I think Mueller has turned out to be a private prosecutor," Giuliani said. "What does this have to do with President Trump? Not a single thing. It has nothing to do with collusion, some guy who donated to the inauguration? My goodness,they had 500,000 people donate to the inauguration -- every time they get a speeding ticket is Mueller going to do it?"

CNN previously reported that Russian oligarchs have also been questioned about donations to the Trump campaign and inauguration.

Guilty for Lobbying

Overall, Patten, 47, was paid more than $1 million for his Ukrainian opposition bloc work including meeting with members of the executive branch, Senate Foreign Relations Committee members and members of Congress, according to a charging document filed in the US District Court for the District of Columbia on Friday. He also worked with an unnamed Russian -- believed to be former Trump campaign chairman Paul Manafort's close associate Konstantin Kilimnik -- to place op-ed articles in US media in 2017, the Justice Department says.

The plea deal was handled by the DC US Attorney's Office and the Justice Department's National Security Division, not Mueller's team, which is about to take former Trump campaign chairman Paul Manafort to trial on a similar charge.

The criminal charging document does not name Manafort or any of his colleagues in the US and Ukraine, though Patten's efforts from 2014 on may be connected to those efforts.

Kilimnik, a Russian national with ties to the Russian military intelligence group accused of interfering in the presidential election, has close professional ties to both Patten and Manafort as they worked for the same Ukrainian political interests.

Kilimnik was among the alleged co-conspirators that helped Manafort hide his Ukrainian consulting income in foreign bank accounts, according to documents revealed at Manafort's trial for financial crimes earlier this month. Mueller's prosecutors charged Kilimnik and Manafort in June in a separate federal court with witness tampering, after Kilimnik reached out to potential witnesses in Manafort foreign lobbying case. Kilimnik has not entered a plea in his case, because he is living in Moscow, prosecutors say. Manafort has pleaded not guilty to the foreign lobbying charges, and those criminal allegations do not reach past 2015.

Kilimnik co-ran a company with Patten, called Begemot Ventures International, according to business records. According to the court filing in the Patten case Friday, Patten and Foreigner A "formed a company in the United States and were 50-50 partners. Beginning in or around 2015, Company A, among other things, advised the Opposition Bloc and members of that part."

As part of his plea, Patten agreed to cooperate with both Mueller's office and prosecutors from the DC US Attorney's Office going forward, including turning over documents and testifying at future grand jury hearings or criminal trials.

Lying to Congress

Patten admitted to lying to the US Senate Intelligence Committee in January this year about the inauguration tickets. While testifying, he attempted to hide his connections to the Ukrainian oligarch and the Russian national with whom he worked, prosecutors said.

Patten "intentionally did not provide" the committee documents related to the Ukrainian oligarch's purchase of four Trump inaugural tickets and lied to the Senate Committee about his foreign lobbying work. He also deleted documents "pertinent to his relationships" with the foreign political interests, according to the Justice Department prosecutors.

Senate intelligence Chairman Richard Burr and Vice Chairman Mark Warner said they referred Patten to the Justice Department.

"We can confirm that Mr. Patten produced documents to the Committee and was interviewed by Committee staff," the senators said in a statement. "Due to concerns about certain statements made by Mr. Patten, the Committee made a criminal referral to the Department of Justice. While the charge, and resultant plea, do not appear to directly involve our referral, we appreciate their review of this matter."

Court appearance

Patten appeared in court Friday morning before Judge Amy Berman Jackson, the same judge who is handling Manafort's trial that is scheduled to begin next month.

In court, Patten conveyed the air of a solemn man aware of what he had done.

As Berman Jackson asked him several questions about his willfulness to plead guilty and the rights he will waive, Patten answered her slowly and clearly each time: "Yes, your honor," "I understand, your honor," "I do, your honor."

In a blue shirt and navy suit and tie, the lifelong Washingtonian stood before the judge, nodding often as she spoke to him.

Patten only appeared to stumble in his speech when asked for his plea.

"I would -- I plead guilty to the charge," Patten said to the judge.

Berman Jackson confirmed that he had signed every page of his plea agreement and charging documents with "a squiggle."

A prosecutor from the DC US Attorney's Office read the charging document made public Friday before the hearing, almost word for word. He added no new details when describing Patten's criminal offense, though he added the words more than once that Patten "was working as a foreign agent of the Opposition Bloc."

The Ukrainian political party, called the Opposition Bloc, had deep ties to Russia in the period in which Patten represented them, including many allies of the former Ukrainian President Viktor Yanukovych. The political party formed from the remnants of Yanukovych's base after he was driven out of Ukraine in 2014 and fled to Russia.

Patten's defense attorney declined to comment following the hearing.

The 35-minute court proceeding was sparsely attended by members of the press and court employees, yet members of Mueller's special counsel's office filled a front row of seats. They were lead Manafort prosecutor Andrew Weissmann and FBI agents Omer Meisel and Brock Domin.

After the hearing ended, Weissmann spent several minutes greeting Patten's defense attorney, Stuart Sears, and two prosecutors from other Justice Department offices on the case. Patten stood waiting with his hands crossed in front of him without a smile, and he shook Meisel's hand.

Spokesmen from the special counsel's office and DC US Attorney's Office declined to comment further about the case.

Patten will not be detained until his sentencing. But he will need to give up his passport and must ask the judge for permission to travel outside the Washington metro area. He also must continue to see a psychiatrist or therapist, which he said he currently does regularly for depression and anxiety treatment, and he must avoid alcohol, the judge ordered.

Berman Jackson also spoke on the rarity of a foreign lobbying prosecution. There is no sentencing guideline for this type of case and no analogous guidelines the court can use to determine Patten's sentence.

"That's a little complicated," Berman Jackson said when discussing his potential sentence. "I don't usually have to go into all that."

The prosecutors and defense will give the court a status update in 60 days on Patten's case.