"We would love to support her by arriving and meeting her, but it is impossible now," Butin told Russia's Izvestia newspaper.
Butin noted that despite certain improvement of his daughter's living conditions, she still remained in the regime of administrative segregation, which provided for 22-hour stay in solitary confinement.
According to Butin, his daughter was not allowed to have outdoor exercise, watch TV or read newspapers.
Butina, a recent student and a highly visible political activist, was arrested in Washington, DC in mid-July on suspicions of acting as an agent for a foreign government. She has denied the accusations. Now Butina, who faces up to 15 years in jail, is being held in a prison in the US city of Alexandria, Virginia.