Russia has freed WNBA star Brittney Griner in a dramatic high-level prisoner exchange, with the US releasing Russian arms dealer Viktor Bout, American officials say.

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

The deal, the second such exchange in eight months with Russia, procured the release of the most prominent American detained abroad.

Mr Biden spoke with Griner on the phone Thursday while her wife, Cherelle, was in the Oval Office.

Mr Biden hailed the release of Griner in a tweet, saying she was on a plane home to the US.

“Moments ago I spoke to Brittney Griner. She is safe. She is on a plane. She is on her way home,” Mr Biden tweeted.

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Mr Biden said Griner was in “good spirits” and was relieved to finally be heading home, adding that she would back in the US within 24 hours.

He said the prison swap deal took “painstaking and intense negotiations” and thanked those members of his administration involved.

Griner’s wife, Cherelle, alongside Mr Biden at The White House, also thanked those involved with her wife’s release.

“Over the last nine months you all have been so privy to one of the darkest moments of my life,” she said.

“So today I’m standing here overwhelmed with emotions, but the most important emotion I have is just sincere gratitude.”

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Play Video. Duration: 45 seconds

The moment Brittney Griner and Viktor Bout crossed paths on the tarmac.

Griner is a two-time Olympic gold medallist whose imprisonment on drug charges brought unprecedented attention after she was initially detained in February for arriving in Russia with vape cartridges filled with “hashish oil” a substance illegal in Russia.

She was later found guilty in a Russian court on drug possession and smuggling charges and sentenced to nine years in a penal colony.

Mr Biden’s authorisation to release a Russian felon once nicknamed “the Merchant of Death” underscored the escalating pressure that his administration faced to get Griner home, particularly after her subsequent transfer to a penal colony.

One of world’s most prolific arms dealers

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Play Video. Duration: 48 seconds

Russian arms dealer Viktor Bout reunites with family after prisoner swap.

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

Russian and US officials had conveyed cautious optimism in recent weeks after months of strained negotiations, with Mr Biden saying in November that he was hopeful that Russia would engage in a deal.

Even so, the fact that the deal was a one-for-one swap was a surprise given that US 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 US government has said are baseless.

Mr Biden said officials were still trying to secure the release of Mr Whelan.

“Sadly and for totally illegitimate reasons, Russia is treating Paul’s case differently from Brittney’s,” he said.

“And while we have not yet succeeded in securing Paul’s release, we are not giving up. We will never give up.”

In releasing Bout, the US freed a 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 US officials said were to be used against Americans.

A man in an orange prison outfit and flak jacket is escorted by police in black military gear
Nicknamed the Merchant of Death, arms dealer Viktor Bout was released in the prisoner swap.(Reuters: Sukree Sukplang)