As news broke that US basketball star Brittney Griner had been released from a Russian prison in exchange for Viktor Bout — a former arms dealer known as the "Merchant of Death" — US officials didn't mince words.
"This was not a choice of which American to bring home. The choice was one or none," US Secretary of State Antony Blinken told reporters.
He was referring to a decision to omit Paul Whelan, 52, a former US marine turned corporate security executive, who is currently serving a 16-year sentence in Russia on espionage charges (which he denies).
"I wholeheartedly wish that we could have brought Paul home today on the same plane as Britney," Mr Blinken said. "But we will stay at it."
Here's what we know about the case.
Who is Paul Whelan and why is he in prison?
Born in Canada and a citizen of four countries, Whelan is a former US marine who served from 2003 to 2008, before being dishonourably discharged for larceny and other lesser offences.
At the time of his arrest in Russia, he was head of global security for BorgWarner, a Michigan car parts supplier.
Whelan was detained by agents from Russia's Federal Security Service (FSB) in a room in Moscow's Metropol Hotel, near the Kremlin, just days after Christmas in 2018.
Investigators said he was a spy for military intelligence with a rank of colonel or higher, and had been caught red-handed with a computer flash drive containing classified information.
Whelan said he had been in Russia for a friend's wedding and had been given the drive in a sting by a Russian friend, claiming that he had thought it contained holiday photos.
After a trial held entirely behind closed doors that US diplomats described as unfair and opaque, Whelan was convicted of spying in 2020, and sentenced to 16 years in a maximum security jail.
He is currently being held in the IK-17 penal colony in the Mordovia region, east of Moscow.
Why wasn't he included in the prison swap?
According to US Secretary of State Antony Blinken, authorities "didn't want to lose the opportunity to secure the release of one of them", describing the situation as "one or none".
"We've had the opportunity to speak directly to Paul Wheelan over the last 24 hours. And let me simply say that he's extraordinarily gracious, as well as being extraordinarily courageous," he added.
It was a sentiment echoed by US President Joe Biden, who said the United States would never give up on seeking Whelan's freedom, but that the prisoner swap involving Griner left few options.
"Sadly and for totally illegitimate reasons, Russia is treating Paul's case differently than Brittney's," he said.
"And while we have not yet succeeded in securing Paul's release, we are not giving up."
Have Paul Whelan or his family said anything?
Whelan told CNN he was "greatly disappointed" that more had not been done to secure his release.
"Especially as the four-year anniversary of my arrest is coming up," he said.
"I would say that if a message could go to President Biden, that this is a precarious situation that needs to be resolved quickly."
Whelan added he had been "led to believe that things were moving in the right direction and that the governments were negotiating and that something would happen fairly soon".
His brother, David Whelan, said a US official had visited family members prior to the prisoner exchange — a decision that he said softened the blow of knowing his brother would stay jailed.
What happens now?
Speaking after the prisoner exchange, an official for the Biden administration said the US had proposed multiple options for Whelan's release, with officials speaking to him "at length" about the Griner deal.
But while Mr Biden has vowed the US would "never give up" on freeing him, David Whelan isn't so confident about the fate of his brother.
"I think we all realise that the math is not going to work out for Paul to come home anytime soon, unless the US government is able to find concessions," he said.
"And so I think we aren’t really sure what the way forward is."
ABC/wires
