The charges against Manafort are related to his Ukrainian consulting work - not Russian interference in the 2016 presidential election, which is the central issue in the special counsel's investigation.
According to court documents, Manafort has agreed to cooperate with Mueller "in any and all matters as to which the government deems the cooperation relevant".
Manafort refused for months to assist Mueller's inquiry before admitting guilt to criminal charges that he concealed money from tax authorities.
Manafort is expected to appear in a USA district courtroom in Washington, D.C., later Friday morning.
There was no sentencing Friday, and Manafort is still detained in prison in Alexandria.
Over the past several months, Manafort's legal options slimmed as the special counsel notched several wins against him, including sending him to jail, securing several cooperators and gaining convictions. His silence had earned him plaudits from the president, and there has been speculation that he was waiting on a pardon from Trump at some later date.
As a political consultant in Ukraine and former business partner of Russian oligarchs, Manafort had a network of relationships in the former Soviet bloc that could shed light on the Russian effort to interfere in the 2016 presidential election.
In the Washington case, prosecutors were set to lay out in great detail Manafort's political consulting and lobbying work on behalf of former Ukrainian President Viktor Yanukovych and the pro-Russian Party of Regions.More news: Greek cliff collapses on popular beach, injuring seven
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During Manafort's Virginia trial, the president had spoken spoke warmly of him.
The federal government's statement of offense against Paul Manafort was released Friday, outlining the evidence underlying their case. In comments to Politico before the plea deal, Giuliani said a plea without a cooperation agreement wouldn't foreclose the possibility of a pardon.
Manafort was convicted last month on eight counts of fraud, bank fraud and failing to disclose banks accounts. "If Manafort says anything that's false, everything, everything goes away, including this plea agreement".
MSNBC's Steve Kornacki asked the Harvard Law professor on Friday about the news that the former Trump campaign chairman is pleading guilty to the charges against him as part of a cooperation agreement with Robert Mueller.
Manafort is the fifth Trump aide to plead guilty in connection to the special counsel's probe.
"Manafort cheated the United States out of over $15 million in taxes", the filing states, adding that in order to commit the crimes, he relied on help from both his longtime deputy Rick Gates and the Russian Konstantin Kilimnik.
Prosecutors had accused him of hiding from U.S. tax authorities $US16 million ($22 million) he earned as a political consultant in Ukraine to fund an opulent lifestyle and then lying to banks to secure $US20 million ($29 million) in loans. The president agreed to wait at least until the investigation concludes, Giuliani has said. He sat straight or leaned his chin on his right hand throughout a lengthy recital of the charges to which he pleaded guilty.
Moscow rejects the conclusions of USA intelligence agencies that it interfered in the American democratic process and Trump denies campaign collusion.