One day after lawyers confirmed that U.S. basketball star Brittney Griner had been transferred to a penal colony outside Moscow, Russia today reiterated its openness to a prisoner exchange with the United States involving notorious convicted arms dealer Viktor Bout.

The fate of Griner, who was arrested on drug charges in a Moscow airport days before Russia invaded Ukraine, has been intertwined with a confrontational tug-of-war between Moscow and Washington. U.S. officials have accused Russia of using Griner and other Americans in Russian custody as bargaining chips.

The Biden administration has been under pressure from Griner’s wife and supporters to work more aggressively to secure her release. In July, the administration proposed a prisoner swap that involved trading Bout for Griner, but Russian officials said it was premature to discuss a deal until the legal process was completed. Griner’s transfer to a penal colony marked that milestone.

Sergei Ryabkov, Russia’s deputy foreign minister, today told journalists that Moscow and Washington were “working professionally along the specifically designated channel” and that he hoped the prospect of a prisoner exchange involving Bout “not just remains but also strengthens.”

“We have yet to arrive at a common denominator, but there is no doubt that Viktor Bout is among those discussed,” he said, according to Interfax, a Russian news agency. “We are definitely counting on a positive outcome.”

Bout is serving a 25-year sentence in a U.S. prison for conspiring to sell weapons to people who said they planned to kill Americans. Since his arrest in 2008, Russia has repeatedly made efforts to secure his release.

The harshness of Griner’s sentence — nine years in prison after she pleaded guilty to a drug charge related to hash oil found in her luggage — led the U.S. government and Griner’s supporters to decry the case as politically motivated. In recent years, Moscow has been accused of collecting foreign prisoners to be used in potential exchanges for Russian inmates abroad.

In addition to Griner’s case, the Biden administration has been working to secure the release of Paul Whelan, a former Marine who in 2020 was sentenced to 16 years in a high-security Russian prison on espionage charges.

The release of Trevor Reed, a former U.S. Marine, as part of a prisoner exchange with Russia in April raised hopes that diplomatic efforts could still yield results despite the current level of hostility between Washington and Moscow.

This article originally appeared in The New York Times.