(NewsNation) — In remarks announcing that WNBA star Brittney Griner has been released from Russia in a prisoner swap, President Joe Biden said that his administration has “not forgotten about Paul Whelan.”

U.S. officials had for months expressed their determination to bring home both Griner and Whelan, a Michigan corporate security executive serving a 16-year sentence in Russia on espionage charges. The U.S. calls these charges politically motivated.

Griner, who was freed Thursday, had been serving a sentence in a Russian penal colony after customs agents say they found cannabis oil inside her luggage at Moscow’s airport in February.

She was freed in an exchange in which the United States released convicted Russian arms dealer Viktor Bout.

Biden maintained on Wednesday that Griner’s release does not mean they aren’t still working on Whelan’s as well.

“This was not a choice of which American to bring home,” Biden said.

For “totally illegitimate reasons,” the president said, Russia is treating Whelan’s case differently than Griner’s.

“While we have not yet succeeded in Paul’s release, we are not giving up,” Biden said. “We will never give up.”

Negotiations are always difficult, Biden noted, and there are never any guarantees during the process.

“We’re going to continue to work to bring home every American who continues to endure such an injustice,” he said. “We also want to prevent any more American families from suffering this pain of separation.”

Paul’s brother, David Whelan said on “NewsNation Live” that the family heard Thursday morning that he would not be coming home.

“The Russian government was not budging on this case,” David Whelan said. “And it was prolonging Miss Griner’s detention and her agony over there to put it off any longer. So I think we’re glad that they decided to make that decision. The sooner that anybody gets free, the better.”

At the same time, David Whelan said, it makes him realize that U.S. officials have run through the list of concessions they can make to the Russian government — which hasn’t taken any of them.

A senior Biden administration official said Biden made the “difficult decision” within the last week to accept the one-to-one prisoner swap, adding that the Russians made it clear that was the only way an exchange would be made.

“I’m not sure what’s next,” David Whelan said.

Brittney Griner’s wife, Cherelle, acknowledged that Paul Whelan is still in Russia during a Thursday news conference.

“Today, my family is whole,” Cherelle Griner said. “But as you all are aware, there are so many other families who are not whole…. BG is not here to say this, but I will gladly speak on her behalf and say that BG and I will remain committed to the work of getting every American home including Paul, whose family is in our hearts today.”

A senior U.S. official spoke with Paul Whelan in prison about Griner’s release.

“While we celebrate Britney’s homecoming, we remain committed to seeing Paul Whelan likewise released,” they said.

This story is developing. Refresh for updates.

The Associated Press contributed to this report.