The administration of United States President Joe Biden has offered to exchange a prisoner in return for the release of basketball star Brittney Griner and a fellow American held by Russia.

A senior official within the administration said a plan had been discussed for a “number of weeks” as reported by CNN.

The administration has offered to exchange Viktor Bout, a convicted Russian arms trafficker serving a 25-year sentence, in return for the release of Griner and Paul Whelan, who has been held by Russia for alleged espionage since 2018.

Griner was detained in February for bringing a vape with cannabis oil into the country, on her way to competing in the Russian basketball league for UMMC Ekaterinburg during the Women’s National Basketball Association off-season.

Griner has already admitted carrying the substance in vape cannisters, but has claimed that they ended up in her luggage inadvertently because she was in a rush.

“We communicated a substantial offer that we believe could be successful based on a history of conversations with the Russians,” the unnamed official told CNN.

“We communicated that a number of weeks ago, in June.”

Although the official did not comment on the specifics of the offer they added: “[It is in Russia’s} court to be responsive to it, yet at the same time that does not leave us passive, as we continue to communicate the offer at very senior levels.”

Secretary of State Anthony Blinken said he expected to discuss the matter on a call with Russian Foreign Minister Sergey Lavrov later this week.

Griner had written to Biden earlier this month urging him not to forget her, with Biden replying to say he was “exhausting all efforts” to bring the player home.

Griner was a part of the United States women’s basketball team that won gold medals at Rio 2016 and Tokyo 2020.