Steven Lalas, 54, was sentenced in 1993 to 14 years in prison for spying, and was placed on parole following his release from a U.S. federal prison.
Lalas is due to arrive in Greece on Sunday, to be reunited with his wife and children, the Justice Ministry said.
"Justice Minister Sotiris Hadjigakis has provided written assurances to the competent U.S. authorities, that the Greek government will fulfill any court decision regarding Mr. Lalas' parole," a statement said.
It said his parole officially expires on July 8, 2010.
Russia has been developing an energy module on the basis of the megawatt-class nuclear power plant since 2010. The spaceship needs neither sunlight nor solar batteries
There are legitimate authorities in Donetsk and Luhansk republics now, with which Russia can implement the project of the economic integration of the Donbass
Austria does not intend to expel Russian diplomats because of the spy scandal