WASHINGTON – A prominent law firm linked to former Trump campaign chairman Paul Manafort's unregistered lobbying effort in Ukraine has agreed to pay $4.6 million as part of a deal with the Justice Department.

Skadden, Arps, Slate, Meagher & Flom LLP was hired by Manafort in 2012 to write a report justifying the prosecution of former Ukraine Prime Minister Yulia Tymoshenko in the midst of a public relations campaign to boost the standing of then-Ukraine President Viktor Yanukovych, an ally of the Kremlin.

At the time of the work, the law firm had not registered with the Justice Department that it was serving as an agent for Ukraine, in violation of the Foreign Agents Registration Act (FARA).

Manafort is scheduled to be sentenced next month in an Alexandria, Virginia, federal court on financial fraud convictions related to his work in the Ukraine. He also pleaded guilty to conspiracy and obstruction of justice in Washington, D.C., and is set to be sentenced there in March after an agreement to cooperate with prosecutors collapsed. The cases against Manafort were brought by Russia special counsel Robert Mueller's prosecution team.

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The Thursday agreement involving the law firm was announced by Justice Department Assistant Attorney General John Demers, chief of the national security division.

Under the agreement, the law firm agreed to pay $4.6 million – representing the amount it received for its work – to the U.S. Treasury. It also will register as a foreign agent with the Justice Department. At the time of the firm's involvement in the Ukrainian campaign, a Skadden partner made "false and misleading statements" to Justice officials about its work, according to federal authorities.

"Law firms should handle inquiries from the federal government the same way they would counsel their clients to: with appropriate due diligence to ensure the honesty of their response," Demers said in a statement.

In a statement, the firm said that the settlement brings "closure" to the civil case.

"As part of this resolution, the firm will be registering with the FARA Unit of the Department of Justice in connection with the work we conducted and will pay to the U.S. Treasury funds we were paid for that engagement. We have learned much from this incident and are taking steps to prevent anything similar from happening again."