Russia freed WNBA star Brittney Grine r on Thursday in a high-profile prisoner exchange, as the U.S. released notorious Russian arms dealer Viktor Bout but failed to win freedom for another American, Paul Whelan, who has been jailed for nearly four years.

The deal, the second in eight months amid tensions over Russia’s invasion of Ukraine, secured the release of the most prominent American detained abroad and achieved a top policy goal for President Joe Biden. But it carried what U.S. officials described as a heavy price.

“She’s safe, she’s on a plane, she’s on her way home,” Biden said from the White House, where he was accompanied by Griner’s wife, Cherelle, and administration officials.

Biden’s authorization to release Bout, the Russian felon once nicknamed “the Merchant of Death,” underscored the heightened urgency that his administration faced to get Griner home, particularly after the recent resolution of her criminal case on drug charges and subsequent transfer to a penal colony.

Griner is a two-time Olympic gold medalist and Phoenix Mercury pro basketball star, whose arrest in February made her the most high-profile American jailed abroad. Her status as an openly gay Black woman, locked up in a country where authorities have been hostile to the LBGTQ community, injected racial, gender and social dynamics into her legal saga and brought unprecedented attention to the population of wrongful detainees.

The Russian Foreign Ministry confirmed the swap, saying in a statement carried by Russian news agencies that the exchange took place in Abu-Dhabi and that Bout had been flown home.

Biden spoke with Griner who was at an airport in Abu-Dhabi after she was greeted by U.S. officials. She was expected to be back in the U.S. within 24 hours, Biden said. U.S. officials said she would be offered specialized medical services and counseling, but declined to go into specifics citing privacy concerns.

Both Russian and U.S. officials had conveyed cautious optimism in recent weeks after months of strained negotiations, with Biden saying in November that he was hopeful that Russia would engage in a deal now that the midterm elections were completed. A top Russian official said last week that a deal was possible before year’s end.

Even so, the fact that the deal was a one-for-one swap was a surprise given that U.S. officials had for months expressed their their determination to bring home both Griner and Paul Whelan, a Michigan corporate security executive jailed in Russia since December 2018 on espionage charges that his family and the U.S. government has said are baseless.

“We’ve not forgotten about Paul Whelan,” Biden said. “We will keep negotiating in good faith for Paul’s release.”

U.S. officials said they did not see an immediate path to bringing about Whelan’s release, saying Russia has treated his case differently because of the “sham espionage” charges against him. Still, they said they believe communications channels with the Russians remain open for negotiations for his freedom to continue — though it was not yet clear what cost would need to be paid to secure it.

Whelan’s brother David said in a statement he was “ so glad” for Griner’s release but also disappointed for his family. He credited the White House with giving the Whelan family advance notice and said he did not fault officials for making the deal.

“The Biden Administration made the right decision to bring Ms. Griner home, and to make the deal that was possible, rather than waiting for one that wasn’t going to happen,” he said.

In releasing Bout, the U.S. freed a former Soviet Army lieutenant colonel whom the Justice Department once described as one of the world’s most prolific arms dealers. Bout, whose exploits inspired a Hollywood movie, was serving a 25-year sentence on charges that he conspired to sell tens of millions of dollars in weapons that U.S officials said were to be used against Americans. Biden issued an executive grant of clemency to free the arms dealer from a federal prison in Illinois to effect the prisoner swap.

The exchange was carried out despite deteriorating relations between the powers prompted by Moscow’s war against Ukraine.

Over the summer, the imprisonment of Americans produced a rare diplomatic opening, yielding the highest-level known contact between Washington and Moscow — a phone call between Secretary of State Antony Blinken and Russian Foreign Minister Sergey Lavrov — in more than five months.

In an extraordinary move during otherwise secret negotiations, Blinken revealed publicly in July that the U.S. had made a “substantial proposal” to Russia for Griner and Whelan. Though he did not specify the terms, people familiar with it said the U.S. had offered Bout.

Such a public overture drew a chiding rebuke from the Russians, who said they preferred to resolve such cases in private, and carried the risk of weakening the U.S. government’s negotiating hand for this and future deals by making the administration appear too desperate. But the announcement was also meant to communicate to the public that Biden was doing what he could and to ensure pressure on the Russians.

Besides the efforts of U.S. officials, the release also followed months of back channel negotiations involving Bill Richardson, the former U.S. ambassador to the United Nations and a frequent emissary in hostage talks, and his top deputy, Mickey Bergman.

Griner was arrested at the Moscow’s Sheremetyevo Airport in February when customs officials said they found vape canisters with cannabis oil in her luggage. She pleaded guilty in July, though still faced trial because admitting guilt in Russia’s judicial system does not automatically end a case.

She acknowledged in court that she possessed the canisters, but said she had no criminal intent and said their presence in her luggage was due to hasty packing.

Before being sentenced on Aug. 4 and receiving a punishment her lawyers said was out of line for the offense, an emotional Griner apologized “for my mistake that I made and the embarrassment that I brought on them.” She added: “I hope in your ruling it does not end my life.”

Her supporters had largely stayed quiet for weeks after her arrest, but that approach changed in May once the State Department designated her as unlawfully detained. A separate trade, Marine veteran Trevor Reed for Konstantin Yaroshenko, a Russian pilot convicted in the U.S. in a cocaine trafficking conspiracy, spurred hope that additional such exchanges could be in the works.

Whelan has been held in Russia since December 2018. The U.S. government also classified him as wrongfully detained. He was sentenced in 2020 to 16 years in prison.

Whelan was not included in the Reed prisoner swap, escalating pressure on the Biden administration to ensure that any deal that brought home Griner also included him.