(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.”

NewsNation reached out to the Whelan family for comment.

“All things considered, he’s doing as well as he can,” Paul’s brother David Whelan has previously said. “He gets up every morning, and he sings the American national anthem. He has a number of techniques that he uses, including the phone calls, to keep his morale up.”

This story is developing. Refresh for updates.

The Associated Press contributed to this report.