"Maria called me today from the prison in Florida," Potapov said. "She said that she is in good spirits."
Potapov noted that he had visited Butina on numerous occasions earlier this year when the US authorities detained her in Alexandria, Virginia.
"The prison in which Maria is serving her sentence now is much more liberal than the one in Virginia. She seems happy, she said the food is good," Potapov said.
Potapov also said Butina is able to make phone calls from prison, but the allowed calling time is very limited.
"She needs to be very careful about the minutes she spends calling," he said.
Maria said that a couple of friends had come to visit her and an Orthodox priest from Florida is trying to arrange to minister her, Potapov added.
On April 26, a US federal judge sentenced Butina to 18 months in prison after she pleaded guilty to a single count of conspiring to act as an unregistered foreign agent in the United States. Butina, who signed the plea deal after being held for prolonged periods in solitary confinement, had requested a sentence of time served.
The Russian Foreign Ministry has called Butina's sentence a disgrace of the US judicial system and has accused the court of carrying out a political order. Russian President Vladimir Putin said Butina’s indictment is unjustified because she was not tasked to perform any mission on behalf of the Russian government.
Butina is eligible for release on 25 October, the Federal Bureau of Prisons said.