Robert O'Brien, who served as national security adviser under President Donald Trump, says that in October 2020 Russia was open to freeing imprisoned Americans Paul Whelan and Trevor Reed to improve relations between the two countries, The Hill reports.

The deal fell through, O'Brien said, when Joe Biden was declared the winner of the presidential election in November.

"Once we lost the election, the Russians lost all interest" in negotiations with the Trump administration, O'Brien told The Hill.

The Biden administration was able to free WNBA star Brittney Griner last week in a trade for Russian arms dealer Viktor Bout. The White House said it tried to free Whelan, a Marine veteran charged with spying, which he denies, but the Russians said it was Griner or no one so they took the deal.

Trevor Reed, who was convicted of hitting a Russian police officer while drunk, was freed earlier this year.

Republicans have been critical of Biden for not getting Whelan released, but Trump posted on Truth Social on Sunday that when he was in office he turned down a one-on-one swap between Whelan and Bout, nicknamed the "Merchant of Death."

"I wouldn't have made the deal for a hundred people in exchange for someone that has killed untold numbers of people with his arms deals," Trump said in the post.

Whelan's sister, Elizabeth Whelan, told The Hill that Trump's statement "was a surprise and not a welcome one." She said the family was unable to have meaningful contact with Trump's National Security Council after O'Brien took over the position from John Bolton.

O'Brien told The Hill that he believed he had a commitment from Russian National Security Adviser Nikolai Patrushev to release Whelan and Reed if the Kremlin could get scheduling summits between Washington and Moscow.

There was no discussion to release Bout, O'Brien said.