Negotiator and former US politician Bill Richardson announced on Thursday the release of a US Navy soldier who had been held in Russia's Kaliningrad territory for nine months.

Taylor Dudley had been detained since April 2022 and was one of several detained Americans sought by Richardson and US authorities.

Dudley, 35, had crossed into Kaliningrad, an exclave between Poland and Lithuania, from Poland where he had been allegedly attending a music festival, according to CNN.

"It is significant that despite the current environment between our two countries, the Russian authorities did the right thing by releasing Taylor today," Richardson said in a statement.

The release came one month after Washington swapped jailed Russian arms dealer Viktor Bout for US basketball star Brittney Griner.

Richardson made no mention of any swap involved in his release.

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He revealed that a team from the Richardson Center, which has assisted in the release of detained Americans from a variety of countries, had visited Moscow several times in the last year to discuss Dudley's case.

"The negotiations and work to secure Taylor's safe return were done discreetly and with engagement on the ground in both Moscow and Kaliningrad and with full support from Taylor's family back in the United States," the statement said.

Richardson spoke in the event of "Taylor's safe return" and expressed concern for Paul Whelan. 

Whelan is a former US Marine who was arrested in Moscow in 2018 and convicted of spying.

The US claims he was a private citizen visiting Moscow on personal business and has demanded his release. He was sentenced in 2020 to 16 years in a Russian prison.

US efforts to negotiate his release as part of the Griner deal fell through after Moscow demanded the release of a Russian former intelligence official imprisoned in Germany.

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