WASHINGTON — Rick Gates, a former Trump campaign aide indicted Oct. 27 with Paul Manafort on charges of money laundering and illegal foreign lobbying, will plead guilty and cooperate with special counsel Robert Mueller, the Los Angeles Times reported.

Gates will admit to fraud-related charges in the next few days and agree to testify against Manafort, who worked for several months as Donald Trump’s campaign chairman in the 2016 presidential election, the paper reported, citing people familiar with the case whom it did not identify.

Two of Mueller’s prosecutors, Andrew Weissmann and Greg Andres, negotiated the Gates deal in recent weeks with Washington defense attorney Thomas C. Green, according to the newspaper. Mueller, who is investigating Russian meddling in the election, leads the prosecution of Manafort and Gates.

Mueller on Friday obtained an indictment of 13 Russian nationals and a so-called troll farm for a broad campaign to sway the 2016 election. And he has secured cooperating guilty pleas from Michael Flynn, Trump’s first national security adviser, and George Papadopoulos, a former policy adviser to Trump’s campaign.

A California man, Richard Pinedo, pleaded guilty to identity theft and is cooperating with Mueller’s prosecutors.

By securing a guilty plea from Gates, Mueller will significantly increase the pressure on Manafort, said Robert Mintz, a former federal prosecutor.

“Gates, by all appearances, worked hand-in-glove with Manafort, and it appears that he’s in a position to provide prosecutors with a treasure trove of evidence and corroboration in their case against Manafort,’’ said Mintz, of McCarter & English LLP.

“Prosecutors build their cases by assembling them one block at a time,’’ Mintz said. “If Gates is able to put pressure on Manafort, prosecutors are no doubt looking to ultimately persuade Manafort to also plead guilty and cooperate. That’s where prosecutors are aiming.’’

A spokesman for Mueller and an attorney for Gates declined to comment on Sunday. An attorney for Manafort didn’t immediately respond to a request for comment.

As Manafort’s longtime deputy, Gates can serve as a narrator for prosecutors at a trial, giving jurors an insider’s account of complex transactions and e-mails, said former federal prosecutor Lee Vartan. Gates can also provide critical leverage because he “will know where all the skeletons are buried,’’ Vartan said.

“If Mueller’s goal is to go above Manafort and infiltrate the Trump administration, then obviously prosecutors want to put pressure on Manafort to break and see if he has information about members of the Trump family or the president himself,’’ said Vartan, who is now at Chiesa Shahinian & Giantomasi.

The pressure on Manafort intensified in a court filing unsealed late Friday. Prosecutors said in the document that he engaged in a “series of bank frauds and bank fraud conspiracies’’ that were not charged in his indictment.

Those alleged frauds relate to a mortgage on a Virginia property that Manafort seeks to pledge to secure his $10 million bail, the filing says. Manafort “provided the bank with doctored profit and loss statements’’ from his company for 2015 and 2016, while “overstating its income by millions of dollars,’’ prosecutors said. 

Green hasn’t entered an appearance in the case, but he participated with Gates at a closed-door hearing with the judge in Washington on Feb. 14. Three other lawyers who represent Gates have told the judge that they want to leave, but the judge hasn’t yet allowed that.

Gates, in court filings, has said he’s under financial distress and is needed at home in Richmond, where he lives with his wife and four children. 

Manafort and Gates are accused of failing to register as agents in the United States for political consulting they did in Ukraine for pro-Russian politicians, conspiring to launder millions of dollars, and hiding offshore bank accounts.

Manafort is accused of laundering money to buy houses, cars, clothes, and landscaping services.

Both men have pleaded not guilty.

In the 37-page indictment revealed by Mueller’s office on Friday, prosecutors targeted three Russian companies and 13 individual Russian associates. The details of the indictment underscore the sophistication and ambition of the Russian attempt to undermine the 2016 US elections.

The secretive, multimillion-dollar disinformation campaign, which US officials said was called the Translator Project, sought to discredit Democrat Hillary Clinton, bolster Republican Donald Trump, and turn Americans against each other.

Allegedly leading this effort was the Russian oligarch Yevgeny Prigozhin, who is often called ‘‘Putin’s chef’’ because of his close ties to President Vladimir Putin.

In December, US intelligence officials concluded that Putin’s top aides had to approve, if not directly oversee, Prigozhin’s operation, according to a classified report from the National Security Agency, parts of which were shared with The Washington Post.

MORE TWEETS FROM TRUMP — The president, who has in the past said he believes Russian President Vladimir Putin’s denials, blamed President Obama and the Democrats for failing to stop Russian meddling. A7

►President says Obama failed to stop Russian meddling. A7