Originally Published: 08 DEC 22 08:06 ET

Updated: 08 DEC 22 10:08 ET

By Jennifer Hansler, Kylie Atwood, Jeremy Herb and MJ Lee, CNN

(CNN) -- WNBA star Brittney Griner has been released from Russian detention, President Joe Biden said Thursday.

Griner was released in a prisoner swap that involved Russian arms dealer Viktor Bout, a source familiar with the matter told CNN. The swap did not include another American that the State Department has declared wrongfully detained, Paul Whelan.

"She's safe, she's on a plane, she's on her way home," Biden said at the White House Thursday morning alongside Griner's wife, Cherelle. "After months of being unjustly detained in Russia, held under untolerable circumstances, Brittney will soon be back in the arms of her loved ones, and she should have been there all along."

Biden acknowledged that Griner's release was occurring while Whelan remained imprisoned, saying that Whelan's family "have to have such mixed emotions today."

"This was not a choice of which American to bring home," Biden said. "Sadly, for totally illegitimate reasons, Russia is treating Paul's case differently than Brittney's. And while we have not yet succeeded in securing Paul's release, we are not giving up. We will never give up."

Griner's February arrest in Russia sparked diplomatic drama between the US and the Kremlin that played out alongside Russia's war in Ukraine. At the same time that the US enacted crippling sanctions in response to the Ukraine war, US diplomats kept open lines of communication with Moscow over prisoner negotiations to try to secure the release of both Griner and Whelan.

Biden said efforts to bring Griner home took "painstaking and intense negotiations" as he thanked members of his administration who were involved.

"This is a day we've worked toward for a long time. We never stopped pushing for her release," he said.

Asked when Griner would be home following his remarks, Biden indicated it would be in the next "24 hours." As for what he would say to Whelan's family, he said, "We're speaking to them."

Cherelle Griner thanked the administration for helping secure her wife's release and said she was "overwhelmed with emotions."

Both she and Brittney Griner "will remain committed to the work of getting every American home, including Paul, whose family is in our hearts today," she added.

Brittney Griner -- who, for years, had played in the off-season for a Russian women's basketball team -- had been detained since February, when she was arrested on drug smuggling charges at an airport in the Moscow region. Despite her testimony that she had inadvertently packed the cannabis oil that was found in her luggage, she was sentenced to nine years in prison in early August and was moved to a penal colony in the Mordovia republic in mid-November after losing her appeal.

'The only deal we could make right now'

Biden gave final approval for the prisoner swap freeing Griner over the past week, an official familiar with the matter said, adding that Biden was updated on the swap as it was taking place Thursday morning.

He was briefed throughout the morning as he awaited confirmation that Griner was back in US hands, a US official says. Once that happened, Biden spoke with Griner from the Oval Office, with Cherelle Griner, Vice President Kamala Harris and Secretary of State Antony Blinken was also on the call, a second official said.

Biden was "personally involved and in constant touch" with his team as this deal came together in the final days and after he gave his personal green light to execute the trade. The briefings -- and questions Biden asked his team -- were constant, a senior administration official says.

The official added that this was the right deal to make, while adding that it was "the only deal we could make right now."

The Russians signaled recently that they were only willing to negotiate for Griner and not Whelan, a US official said. That is because Russia has been handling their cases differently based on what each has been accused of.

The Biden administration repeatedly made offers to get Whelan released as part of this deal, even after Russia made clear only Griner was acceptable.

In the end, when it was clear Russia was going to refuse on Whelan, the US had to accept it.

"It was a choice to get Brittney or nothing," the US official said.

The official says that was a "difficult decision" for Biden, but again, one he felt he had to make.

Whelan family 'devastated'

Whelan, a US, Irish, British and Canadian citizen, was detained at a Moscow hotel in December 2018 by Russian authorities who alleged he was involved in an intelligence operation. He was sentenced to 16 years in prison on espionage charges he has vehemently denied. Whelan had been carrying out his sentence at a different labor camp in Mordovia, an eight-hour drive from Moscow, where he told CNN in June 2021 he spent his days working in a clothing factory that he called a "sweatshop."

Whelan's family expressed happiness at the news that Griner is on her way home but said Thursday they are "devastated" that he was left behind.

"It's a great day for the families of the wrongfully detained and we feel wonderful for them," David Whelan, Paul's brother, said on "CNN This Morning." "But we do worry about what's in Paul's future. I think it's become clear that the US doesn't have any concessions that the Russian government wants for Paul. So I'm not really sure what the future holds."

The Biden administration told Whelan's family ahead of the Griner announcement, David Whelan said.

In an email to the media, David Whelan said his family was "devastated" at the news and increasingly worries that Paul won't survive the rest of his sentence.

Earlier this year, after the US secured the release of Trevor Reed, another American who'd been detained in Russia since 2019, Paul Whelan expressed frustration through a statement shared by his parents.

"Why was I left behind?" Whelan said in April. "While I am pleased Trevor is home with his family, I have been held on a fictitious charge of espionage for 40 months."

'Merchant of Death' included in swap

Bout has returned home to Russia, the Russian foreign ministry said Thursday. The prisoner exchange with Griner was "completed successfully at Abu Dhabi Airport" on Thursday, state media added.

In his statement Thursday, Biden thanked the United Arab Emirates for its help with the exchange.

The UAE and Saudi Arabia said in a joint statement that the two countries were involved in joint mediation efforts leading to the prisoner swap. The statement said that the "success of the mediation efforts is a reflection of the mutual and solid friendship that connects both countries with the United States of America, and the Russian Federation."

Bout, nicknamed the "Merchant of Death," is a former Soviet military officer serving a 25-year prison sentence in the United States on charges of conspiring to kill Americans, acquire and export anti-aircraft missiles, and provide material support to a terrorist organization. Moscow had slammed his sentencing in 2012 as "baseless and biased" and Bout has maintained he is innocent.

Steve Zissou, Bout's lawyer in the US, told CNN on Thursday that the prisoner swap between Griner and his client was "fair."

"As I have urged for some time, given the 15 long years that Viktor Bout has been in custody since the United States government targeted him in 2006, his exchange for Brittney Griner, who has only been in custody for a few months, is fair," Zissou said in a statement.

Zissou told CNN said that his legal team knew a swap was imminent 24 hours ago.

This story has been updated with additional developments.