Paul Whelan, a former US Marine accused of spying and arrested in Russia ,stands inside a defendants' cage during a hearing at a court in Moscow on August 23, 2019.
Washington CNN  — 

The Biden administration believes the Russian government will continue to engage on detainee issues, including freeing American Paul Whelan, following the release of WNBA star Brittney Griner because “they have things they want in this world,” a senior administration official told CNN.

Moscow knows that ultimately the two sides will reach “a mutually acceptable arrangement if they keep talking to us,” the official continued.

“We have shown an openness to talk about that which is actually available to us and gotten only in response a demand for something not available to us,” the official said, reiterating that the Russians refused what had been offered to secure the release of Whelan.

On Friday, Russian President Vladimir Putin said that further prisoner swaps with the United States are possible. Putin said the exchange of Griner for convicted Russian arms dealer Viktor Bout “is the result of negotiations and the search for compromises.”

“In this case, compromises were found. We do not refuse to continue this work in the future,” he said.

CNN previously reported that convicted Russian murderer Vadim Krasikov, who is in German custody, was one of Moscow’s requests, and the official did not rule out that his release has been a continued request.

Demands related to the war in Ukraine did not come up in the negotiations to secure Griner’s release and attempt to secure Whelan’s, the official said, adding that the US would not make concessions on that front.

“We’ve obviously thought about why that might be the case” that the Russians didn’t float it, the official said, “and I think we credit it to the fact that we’ve been so crystal clear, so consistent, that it is not for us to negotiate how that horrific situation gets resolved.”

The official added: “If it were raised, of course, it is not for bargaining. Another country’s future is not for bargaining and the defense of democracy against autocracy is not for bargaining.”

Even though US Secretary of State Antony Blinken has said that “every possible” offer was made to the Russians to secure Whelan’s release, the Biden administration has ideas about “new forms of offers” they are going to try with the Russians in an effort to secure Whelan’s release, the senior administration official said.

Whelan told CNN on Thursday that “the President and his team are going to have to look at what they have that is valuable that these people want, and hopefully give it to them, or I’ll be here for a long time.”

His brother, however, has cast doubt on the possibility of identifying something that the Russians want.

“It’s clear that the US government has no concessions that the Russian government will take for Paul Whelan. And so Paul will remain a prisoner until that changes,” David Whelan said in a statement Thursday.

Paul Whelan’s sister, Elizabeth Whelan, said on CNN’s “Erin Burnett OutFront” Friday that the public discussion surrounding a potential swap has “been very difficult for my family to hear,” adding she believes her brother is being “discussed as if his only value was what we would have to give up for him.”

Asked about her family’s discussions with the US government regarding her brother’s imprisonment, Elizabeth Whelan said, “I think we’ve made it pretty clear – that as far as I’m concerned, at least – my brother is worth more, has a greater value than any Russian criminal.”

Russia views Paul Whelan as a spy, the senior administration official explained, which means they treat him in a different category. The official didn’t count out the US offering a Russian spy in US custody as a potential offer to Russia.

“There is a willingness to pay even a very big price on the part of this President,” the official said. “We have made clear to the Russians that we at least are open to talking about that which is at our disposal, that which we could actually deliver. It would be somebody in our custody.”

CNN’s Anna Chernova, Uliana Pavlova and Sonnet Swire contributed to this report.