US President Donald Trump holds up a copy of The Washington Post at the White House in Washington D.C., the United States, on Feb. 6, 2020. Donald Trump took a victory lap Thursday, a day after a divided Senate voted to acquit him on impeachment charges. (Xinhua/Liu Jie)

The US Justice Department abruptly dropped its criminal case Monday against the company controlled by a confidant of Russian President Vladimir Putin that allegedly funded the campaign to meddle in the 2016 presidential elections.

Just weeks before the trial was to begin, the Justice department announced it was withdrawing the eight-count indictment of Concord Management and Consulting, a company owned by close Putin ally Yevgeniy Prigozhin.

Concord, which funds the St. Petersburg-based troll factory the Internet Research Agency, was part of an indictment against 13 Russian individuals and three companies - one of the major outcomes of Special Counsel Robert Mueller's 22-month investigation into Russian interference in the 2016 vote.

The request to drop the case puts a dent in Mueller's prosecutorial successes, though the case had been an uphill battle from the beginning.

The Internet Research Agency, Mueller charged, actively pumped disinformation, memes and fake news into social media through false accounts to influence US voters and tilt the election four years ago to help President Donald Trump.

Like Mueller, US intelligence chiefs concluded that the Concord-run operation was one half of a sweeping campaign overseen by Putin - the other half was hacking by Russian intelligence - to help Trump and hurt his rival, Democrat Hillary Clinton.

In a filing in Washington federal district court, the Justice Department said that Concord's tactics of trying to use US law and court procedure to pry out classified intelligence related to the evidence against it was a threat to national security.

Concord was the only one of 25 Russians and three Russian companies charged by Mueller to be brought to trial. The rest are considered out of reach of US law, but the charges against them - including Prigozhin - remain in place.

The Justice Department said recent rules changes regarding evidence based on classified US intelligence made it harder to proceed in the case without exposing secrets.

Russia does not have an extradition treaty with the US, and the company's executive, Evgeny Prigozhin, a businessman with close ties to Putin, who is also individually charged in the case, was never expected to set foot inside a US courtroom.

Prigozhin and Concord were both charged in 2018, along with 12 other individuals and two other entities, with conspiracy to defraud the US for their alleged role in election meddling aimed at sowing discord in the US.

AFP / Reuters