Former U.S. Marine Paul Whelan was arrested in Russia in 2018. He was eventually sentenced to 16 years in prison on espionage charges.
Earlier this week, the White House acknowledged the four-year anniversary of Whelan's detention in Russia.
National security adviser Jake Sullivan released a fiery statement on Whelan's situation.
"Today marks four years of wrongful detention in Russia for American Paul Whelan and, as the President and I have told the Whelan family, we will not stop, we will not relent, we will not cease until all Americans can celebrate Paul’s return," Sullivan said.
David Whelan also commented on his brother's situation.
"Today is the 1,461st day that Paul has been held hostage by the Russian Federation. Russian authorities entrapped him four years ago today," he wrote. "How do you mark such an awful milestone when there is no resolution in sight?"
The Biden administration tried to secure Whelan's release during previous negotiations with Russia.
Hopefully, the Biden administration can bring Whelan back home sooner than later.