WASHINGTON, D.C.  (TIP):  Brittney Griner, the American basketball star imprisoned in Russia, was released on Thursday, December 8,  after 10 months of captivity after President Biden agreed to a swap for Viktor Bout, an imprisoned Russian arms dealer known as the “Merchant of Death,” the president said.

On Thursday morning, Mr. Biden tweeted a picture of himself and Cherelle Griner, Ms. Griner’s wife, in the Oval Office, with the words: “Moments ago I spoke to Brittney Griner. She is safe. She is on a plane. She is on her way home.”

Paul Whelan, another American held prisoner, was not released on Thursday despite months of efforts by U.S. diplomats to include him as part of the deal with the Russians for the exchange with Mr. Bout.

Ms. Griner, an All-Star center with the W.N.B.A.’s Phoenix Mercury and a two-time Olympic gold medalist, was serving a nine-year prison sentence that put her at the center of a fraught geopolitical showdown between Washington and Moscow. In February, she was stopped at an airport near Moscow after customs officials found two vape cartridges containing hashish oil in her luggage.

Her case became an international cause because she was seen as a hostage held by President Vladimir V. Putin’s government as Russia was subjected to a broad swath of international sanctions in response to its invasion of Ukraine a week after her arrest. The Biden administration’s efforts to negotiate a prisoner swap with Russia for her and Mr. Whelan, had stalled for months as she was sent to a penal colony outside Moscow.

Ms. Griner was described by one of her lawyers this fall as struggling emotionally and increasingly worried that she would not be freed. She was permitted outside once a day to walk for an hour in a small courtyard, according to her lawyer, and otherwise confined to a cramped cell with two cellmates. She slept on a specially elongated bed to accommodate her 6-foot-9 frame.

American officials met with her in the penal colony last month for the first time since a Russian court rejected her appeal and reported that she was doing “as well as can be expected,” as a White House spokeswoman put it at the time. Ms. Griner turned 32 while in custody and her family continued to press for her release.

Mr. Whelan, a former U.S. Marine who later worked as a corporate security executive, was arrested at a Moscow hotel in December 2018 and convicted in June 2020 on espionage charges that the U.S. government says were manufactured. Administration officials sought his release as part of a package deal with Ms. Griner for Mr. Bout.

Officials said Thursday that the Russians refused to include Mr. Whelan as part of the agreement, leaving the president to agree to a “one-for-one” swap much like he did in April when he agreed to release Konstantin Yaroshenko, a Russian pilot, in exchange for Trevor Reed, an ailing former U.S. Marine held for two years on what his family considered to be bogus charges of assault.

The trade for Mr. Bout gave Moscow back one of the most notorious arms dealers of modern times, earning the nickname “Merchant of Death” as he evaded capture for years. He was convicted in 2011 by a New York jury on four counts that included conspiring to kill American citizens. Prosecutors said he had agreed to sell antiaircraft weapons to drug enforcement informants who were posing as arms buyers for the Revolutionary Armed Forces of Colombia.

In July, American officials expressed frustration publicly that their Russian counterparts were refusing to engage in what the officials called a “substantial offer” to secure her release in exchange for Mr. Bout. For months, American diplomats said that Mr. Putin seemed uninterested in even discussing the offer.

Earlier this month, a top Russian diplomat said publicly that the chance for a deal that would free Ms. Griner was increasing. But U.S. officials dismissed his comments, saying that they continued to be stonewalled by the Russians, who were not seriously negotiating a deal for Mr. Bout.