The Kremlin confirmed that Russia is in talks with the United States to exchange prisoners held by each country after the U.S.

state secretary disclosed a “substantial proposal” for a possible swap. Secretary of State Antony Blinken said Wednesday that Washington made the proposal “weeks ago” to facilitate the release of basketball star Brittney Griner and former Marine Paul Whelan.

CNN reported that the Biden administration has offered to exchange Griner and Whelan for convicted arms trafficker Viktor Bout.“A concrete result has not yet been reached,” President Vladimir Putin’s spokesman Dmitry Peskov told reporters at a daily briefing Thursday, in the first indirect public confirmation of the existence of bilateral talks. Russia’s Foreign Ministry said earlier Thursday that President Vladimir Putin and U.S.

counterpart Joe Biden had discussed the possible exchange “at some point” in the future, ordering their respective officials to conduct negotiations. “They’re ongoing.

Nothing has been achieved yet,” the ministry’s spokeswoman Maria Zakharova said in a statement. Griner is currently facing up to 10 years in Russian prison for drug smuggling, a crime she has pleaded guilty to but said she did not commit intentionally. Whelan, who is serving a 16-year prison sentence on espionage charges, has repeatedly maintained that he is innocent.Bout, 55, is the highest-profile Russian prisoner serving time in the U.S.

He inspired the 2005 arms smuggling movie "Lord of War" starring Nicolas Cage. Bout's wife Alla said on Wednesday the gun runner knew nothing about the possible exchange.  The United States and Russia previously carried out one prisoner swap in the heat of the Ukraine war, with Washington exchanging former U.S.

Marine Trevor Reed for convicted drug smuggler Konstantin Yaroshenko in April. AFP contributed reporting.