The Trump administration on Wednesday disavowed its decision to include a Moscow-born American businessman on a public list of Russian "oligarchs," resolving a months-long court fight in which the U.S. Treasury Department was accused of copying a roster of Russian billionaires that Forbes Magazine published in 2017.

The businessman, Dr. Valentin Gapontsev, represented by Norton Rose Fulbright, sued the Treasury Department last year in Washington's federal trial court after being included on a list of purported cronies of Russian President Vladimir Putin. The Treasury Department had been required to compile the list under the Countering America's Adversaries Through Sanctions Act, a sanctions law against Russia, Iran and North Korea that President Donald Trump signed in August 2017 but said was "seriously flawed."

Gapontsev, the founder and chief executive of IPG Photonics, a Massachusetts-based manufacturer of specialized lasers, argued that Treasury Secretary Steven Mnuchin had failed to take up a "serious inquiry" before including him on the purported oligarchs list. Although Gapontsev was not formally sanctioned, he argued his appearance on the list had caused reputational harm and raised complications for IPG Photonics in dealings with customers and financial institutions.

In a letter to Gapontsev's lawyers, the U.S. Treasury Department on Wednesday declared he "is not an oligarch in the Russian Federation." The department said that "if it had to create the unclassified report today" listing Russian oligarchs, Gapontsev would not be included.

"The Department's view is based on information we did not have at the time the report was submitted to Congress. Among other things, Dr. Valentin Gapontsev is a U.S. citizen and chairman and CEO of IPG Photonics Corporation, a publicly-traded corporation headquartered in the United States," wrote Paul Ahern, the acting principal deputy assistant secretary in the Treasury Department's Office of Terrorist Financing and Financial Crimes.

The Treasury Department sent the letter as part of a settlement agreement with Gapontsev, who was represented by Norton Rose Fulbright partners Michael Edney and Stephen McNabb, who leads the firm's international trade group.

"Dr. Gapontsev is not a Russian oligarch; he is a leader of American business and a renowned scientist. He never belonged on the oligarchs list, and today's action makes that clear," Edney, chairman of Norton Rose's white-collar and criminal defense team, said Wednesday in a statement. "We are pleased with today's resolution and grateful to the Treasury and Justice Departments and to the court for working with us to achieve it."

Gapontsev had argued that his identification as a Russian oligarch cast a pall over him and IPG Photonics, prompting at least one customer to assume that the company was "effectively disqualified from doing business with U.S. persons and corporations." His lawyers argued that the "oligarch" label was "no less injurious than being associated with the Soviet government in the 1950s." And they said a third-party trade compliance system, Visual Compliance, "flagged Dr. Gapontsev in its system as posing a problem after the secretary submitted his List of Oligarchs to Congress."

At a court hearing in April before U.S. District Judge Rudolph Contreras of the District of Columbia, a Justice Department attorney did not dispute Gapontsev's claim that the Treasury Department had effectively republished a Forbes list of Russian millionaires and labeled them "oligarchs."

"We're not challenging that assertion," said Justice Department attorney Kevin Snell, after being asked whether it was true that the Treasury Department had copied the names from a Forbes list titled "Billionaires: The Richest People in the World."

A Treasury representative told Forbes last year: "There is not a statutory or regulatory definition of oligarch, so Treasury included the $1 billion threshold as a reasonable number, which is similar to criteria contained in the U.S. Forbes list."

Following that hearing, the two sides entered a mediation process overseen by U.S. Magistrate Judge G. Michael Harvey.

Lawyers in the case on Wednesday asked the judge to stay proceedings for three years.