The court dropped some of the charges leveled against Paul Manafort concerning a Virginia bank fraud case.
"I have not heard any estimation from the government of when his cooperation will be complete," US District Judge T.S. Ellis said, referring to the special counsel investigation. "I'm not willing to go on endlessly" before sentencing Manafort, he added.
Donald Trump’s former campaign manager will be sentenced on February 8 on bank and tax fraud charges.
Addressing the legal battle, the office of Special Counsel Robert Mueller stated that it was not clear when Manafort would complete his cooperation in the probe into Russia's alleged meddling in the 2016 US presidential election.
The directive resulted in numerous charges against Manafort, eight of which he was found guilty of by a Virginia jury in late August.
Moscow has repeatedly denied the accusations of meddling in the US election, stressing that no evidence has been provided to confirm the claims.