The United States pushed Moscow to accept a deal that aims to secure the release of two Americans detained in Russia after one of them, basketball star Brittney Griner, was sentenced on Thursday to nine years in prison on a drug charge.

"It's a serious proposal. We urge them to accept it. They should have accepted it weeks ago when we first made it," said White House national security spokesperson John Kirby, without offering details.

Washington has offered to exchange Russian arms trafficker Viktor Bout, who is serving a 25 year-prison sentence in the United States, for Griner and former U.S. Marine Paul Whelan, sources familiar with the situation have told Reuters.

Russia had tried to add convicted murderer Vadim Krasikov, who is in prison in Germany, to the proposed swap, a source familiar with the proceedings also told Reuters.

When asked on Thursday if Washington would be willing to reconsider Russia's request following Griner's sentencing, Kirby dismissed it: "I don't think we go so far as to even call it a counter-offer."

Whelan, who holds American, British, Canadian and Irish passports, was sentenced in 2020 to 16 years in jail in Russia after being convicted of spying. Griner was convicted and sentenced on Thursday after she was convicted of bringing cannabis-infused vape cartridges into Russia.

President Joe Biden has come under increasing pressure from families of Americans detained abroad to help bring them home. He is "receiving regular updates" about negotiations for the release of Griner, Whelan and others deemed wrongfully detained, said White House spokeswoman Karine Jean-Pierre.

U.S. Secretary of State Antony Blinken spoke on the phone with Russian Foreign Minister Sergei Lavrov last Friday and pressed Russia to take the deal. Kirby said that since then conversations had been ongoing at various levels.

Blinken and Lavrov are currently both in Cambodia for a meeting of the Association of Southeast Asian Nations (ASEAN). Kirby earlier told MSNBC that Blinken will likely try to speak with Lavrov again now Griner had been sentenced.

"They are being wrongfully detained, they need to be let go. They need to come home," Kirby told reporters.

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