Detained American Paul Whelan expressed his frustration that more has not been done to secure his release in an exclusive CNN interview hours after another detained American, Brittney Griner, was freed.

Whelan said he was happy that Griner was released, but told CNN, “I am greatly disappointed that more has not been done to secure my release, especially as the four year anniversary of my arrest is coming up.”

“I was arrested for a crime that never occurred,” he said in a phone call from the penal colony where he is being held in a remote part of Russia. “I don’t understand why I’m still sitting here.”

The interview took place shortly after President Joe Biden, standing alongside Griner’s wife Cherelle at the White House, also expressed regret that the US had not been able to get Whelan out. Biden vowed the US would “never give up” on him. US officials said the Russians refused to negotiate his release.

“This was not a situation where we had a choice of which American to bring home. It was a choice between bringing home one particular American – Brittney Griner – or bringing home none,” a US senior administration official said Thursday morning.

Whelan said he was surprised that he had been left behind.