Russia has freed Brittney Griner in a dramatic high-level prisoner exchange that brings the WNBA star back to the United States after almost 10 months' detention.

The swap, made at a time of heightened tensions over the invasion of Ukraine, achieved a top goal for President Joe Biden but carried a heavy price and left behind Paul Whelan, an American jailed for nearly four years in Russia.

Biden tweeted about Griner's release Thursday morning, writing that she is on her way back to the United States.

Moments ago I spoke to Brittney Griner.

She is safe.
She is on a plane.
She is on her way home. pic.twitter.com/FmHgfzrcDT

— President Biden (@POTUS) December 8, 2022

Biden spoke with Griner on the phone Thursday while her wife, Cherelle, was in the Oval Office. In an address from the White House, Biden said these "past few months have been hell for Brittney" but that she was in good spirits.

"This is a day we've worked toward for a long time," Biden said. "We never stopped pushing for her release. It took painstaking and intense negotiations, and I want to thank all the hardworking public servants across my administration who worked tirelessly to secure her release."

Cherelle Griner also spoke at the White House and thanked a number of people who helped secure her wife's release.

"Today my family is whole," Cherelle Griner said.

The deal, the second such exchange in eight months with Russia, procured the release of the most prominent American detained abroad. Griner is a two-time Olympic gold medalist whose monthslong imprisonment on drug charges brought unprecedented attention to the population of wrongful detainees.

Biden's authorization to release notorious Russian arms dealer Viktor Bout, once nicknamed the Merchant of Death, underscored the escalating pressure that his administration faced to get Griner home, particularly after the recent resolution of her criminal case and subsequent transfer to a penal colony.

Russia's foreign ministry also confirmed the swap Thursday, saying in a statement carried by Russian news agencies that the exchange took place in Abu Dhabi, United Arab Emirates, and that Bout has been flown home.

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 after the U.S. midterm elections. A top Russian official had 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 determination to bring home both Griner and Whelan, a Michigan corporate security executive jailed in Russia since December 2018 on espionage charges that his family and the U.S. government have said are baseless.

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.

The Biden administration was ultimately willing to exchange Bout if it meant Griner's freedom. The detention of one of the greatest players in WNBA history contributed to a swirl of unprecedented public attention for an individual detainee -- not to mention intense pressure on the White House.

Griner's arrest in February made her the most high-profile American jailed abroad. Her status as a gay Black woman, locked up in a country where authorities have been hostile to the LGBTQIA+ community, infused gender, racial and social dynamics into her legal saga and made each development a matter of international importance.

Her case not only brought unprecedented publicity to the dozens of Americans wrongfully detained by foreign governments but also emerged as a major inflection point in U.S.-Russia diplomacy at a time of deteriorating relations prompted by Moscow's war against Ukraine.

The exchange was carried out despite deteriorating relations between the powers. But 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. Although 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, Griner's release followed months of backchannel 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. The men had made multiple trips abroad in the past year to discuss swap scenarios with Russian contacts.

Griner was arrested at 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 that their presence in her luggage was due to hasty packing.

Before being sentenced Aug. 4 and receiving a nine-year 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.

As Griner's detention continued, coaches and players around the WNBA and women's college basketball tried to help keep her case in the spotlight.

"God is good. Prayers are powerful," LSU's Kim Mulkey, who coached Griner at Baylor from 2009 to 2013, told ESPN's M.A. Voepel following news of her former player's release. "Brittney is on her way home where she belongs. Our prayers remain with her and her family as they recover and heal together."

Said Baylor women's basketball coach Nicki Collen in a text to ESPN: "After nearly 10 months, we are thrilled and relieved to hear the long-awaited news of BG's return. Today is the day we've been praying for, and we will continue to pray as she reunites with her family and begins recovering from her experience. Baylor family, she's coming home!"

USA Basketball also celebrated Griner's release in a statement, saying Griner "has shown bravery and resolve over the last nearly 300 days. USA Basketball is relieved that she is on her way home and will happily reunite with her wife, family and friends."

Whelan has also been classified as wrongfully detained by the U.S. government. He was sentenced in 2020 to 16 years in prison. He 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.

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

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.

The Associated Press contributed to this report.