Khodorkovsky and Platon Lebedev, both 43, were sentenced to eight years each for fraud and tax evasion in May 2005.
"The [new] charges will most likely be brought tomorrow," said Vladimir Krasnov, defense counsel for Lebedev.
Prosecutor General Yury Chaika said earlier that Khodorkovsky and Lebedev may face new charges if there is sufficient evidence.
"Investigations into the main [Yukos] case are continuing," Chaika said. "Some of its numerous episodes are already in court."
Prosecutors continue to investigate suspected money laundering in the now bankrupt Yukos Oil Company [RTS: YUKO].
Former Yukos security chief Alexei Pichugin was given 24 years in prison for carrying out two murders and organizing an attempted killing.
The prosecutors opened a new probe in the Yukos case in the summer of 2005.
In July 2005, prosecutors told defense lawyers that Lebedev and Khodorkovsky should be taken to a pre-trial detention center to face new charges, but no charges followed.
