FILE PHOTO: Maria Butina appears in a police booking photograph released by the Alexandria Sheriff's Office in Alexandria, Virginia, U.S. August 18, 2018. Alexandria Sheriff's Office/Handout via REUTERS/File Photo

MOSCOW (Reuters) - Russian national Maria Butina, who was jailed in the United States in April after admitting to working as a Russian agent, will be released from a U.S. prison on Friday and arrive back in Moscow the next day, Russia’s foreign ministry said.

Butina pleaded guilty in December last year to one count of conspiring to act as a foreign agent for Russia, prompting Moscow to accuse Washington of forcing her to confess to what it described as ridiculous charges.

The case has been an irritant in fraught relations between Moscow and Washington that are strained over everything from Syria to the arrest in Moscow of Paul Whelan, a former U.S. Marine held on spying charges that he denies.

Butina, who was arrested in July 2018, was sentenced to 18 months in prison in April after she expressed remorse for conspiring with a Russian official to infiltrate a gun rights group and influence U.S. conservative activists and Republicans.

The 30-year-old Siberian native will be transferred from a federal prison in Tallahassee, Florida before being taken to Miami from where she will fly to Moscow, Russia’s foreign ministry said in a statement on Friday.