A former FBI lawyer will plead guilty to falsifying a document in the first criminal case arising from US Attorney John Durham’s investigation into the probe of ties between the Russian government and Donald Trump’s 2016 campaign, the New York Times reports.

The lawyer, Kevin Clinesmith, will admit he changed an email from the CIA that was used in seeking renewed court permission in 2017 for a secret wiretap on former Trump campaign adviser Carter Page, the Times reported, citing three people familiar with the case.

Kevin Clinesmith is the first person charged by John Durham’s probers. Photo: YouTube

The case against Mr Clinesmith will be cheered by Trump and his supporters, who have long accused the FBI of mounting a covert campaign to bring down America’s 45th president by framing him as a Russian puppet after Hillary Cliton’s stunning loss in the 2016 election.

The investigation by veteran prosecutor Durham, who brought the charge against Clinesmith, is also examining the intelligence community’s assessment about alleged Russian election interference.

The probe has caused deep concern among Democrats who fear criminal charges or public reports issued so close to the 2020 election could affect November’s vote.

Attorney General William Barr foreshadowed the legal action in a Fox News Channel interview on Thursday night in which he said there would be a development on Friday that was “not earth-shattering” but would be an indication that the investigation was moving along.

Legal observers that the first person to be plead guilty in any investigation will likely have cut a deal for a light sentence in return for informing on others.

Justice Department policy directs prosecutors not to take investigative steps for the purpose of affecting an election and frowns upon public actions in the weeks before an election.

But Barr has said he did not feel constrained by that policy in part because the presumptive Democratic presidential nominee, former vice-president Joe Biden, is not a target of Durham’s investigation, and Barr has signalled he will look to make Durham’s findings public before the election.

Clinesmith was referred for potential prosecution by the department’s inspector general’s office, which conducted its own review of the Russia investigation.

-with AAP