A day after the American basketball star Brittney Griner was sent to a Russian penal colony, a top Russian diplomat said on Friday that the prospect of a prisoner exchange was increasing, and acknowledged that it could involve a Russian arms dealer imprisoned in the United States.
But U.S. officials dismissed the suggestion of any new optimism about an agreement, saying that the Kremlin had not been serious about negotiating a deal.
Since June, the Biden administration has been proposing trading Viktor Bout, the arms dealer, for Ms. Griner, who has been jailed for nine months and Paul N. Whelan, an American held for almost four years and convicted of espionage, according to U.S. officials and numerous news media reports.
Their fates have been caught up in the hardening confrontation between Washington and Moscow over the Russian invasion of Ukraine, which American officials say is reflected in the tough treatment of Ms. Griner. She was sentenced to nine years for entering Russia with vape cartridges containing hashish oil, and her lawyers confirmed on Thursday that she had been transferred from a jail to a penal colony, where harsh conditions and mistreatment are commonplace.
U.S. officials have not publicly acknowledged that Mr. Bout has been offered in a prisoner swap, but on Friday, the Kremlin did. “So far, we have not come to a common denominator, but it is undeniable that Viktor Bout is among those who are being discussed, and we certainly count on a positive result,” Sergei A. Ryabkov, the deputy foreign minister, told reporters in Moscow, according to the Interfax news agency.
The chance of an exchange “is being strengthened,” he said, adding that “we are working professionally through a special channel designed for this.” But he did not explicitly say for whom Mr. Bout would be traded, according to Interfax.
The U.S. State Department quickly threw cold water on his comments.
“We have made a substantial offer that the Russian Federation has consistently failed to negotiate in good faith,” a department spokesman, Vedant Patel, said at a news briefing. The U.S. government “has continued to follow up on that proposal and propose alternative potential ways forward.”
But, Mr. Patel said, the Kremlin’s “failure to seriously negotiate on these issues in the established channel, or any other channel for that matter, runs counter to its public statements.”
The diplomatic back-and-forth came on a day when Ukraine’s prime minister, Denys Shmyhal, said that nearly half of his country’s energy grid had been damaged by Russian strikes. Russian forces have launched heavy barrages of missiles and exploding drones at Ukraine’s civilian infrastructure, hoping to break down the country’s ability to function and its will to fight.
Russia’s strategy, Mr. Shmyhal said at a news conference, was “fighting against the civilian population and depriving them of light, water supply, heat and communications during the winter.”
The Russians have suffered serious battlefield setbacks in recent weeks, but the fighting is slowing as cold weather sets in and both sides regroup.
Also on Friday, Swedish investigators said they had found evidence that explosives were used to sever the Nord Stream gas pipelines under the Baltic Sea in September, confirming European officials’ suspicions that it was sabotage. It remains unclear who might have attacked the pipelines, which carried Russian natural gas to Germany until Moscow cut off the flow, or why.
Unable so far to win military victory, the government of President Vladimir V. Putin has sought other forms of leverage against the United States and other nations backing Ukraine — manipulating energy supplies and spreading disinformation — and U.S. officials say that includes using imprisoned Westerners as bargaining chips.
The Biden administration has been under pressure from Ms. Griner’s wife and supporters to work more aggressively to secure her release. The question is whether Mr. Putin would rather keep that pressure on, ensuring one more headache for President Biden and potentially making him look ineffectual, or would prefer to have Mr. Bout.
Ms. Griner, 32, who has won a WNBA championship with the Phoenix Mercury and two Olympic gold medals with U.S. teams, has also played for years in the top Russian women’s league, and was on her way to join her team when she was arrested in February at Sheremetyevo Airport near Moscow.
Russian prosecutors said she was found with less than 0.3 grams of hashish oil. Other foreigners found with small amounts of cannabis have been quickly fined and expelled from Russia, but Ms. Griner’s case was handled differently. She pleaded guilty in July, but the authorities went ahead with the proceedings, and a court sentenced her in August to nine years in a penal colony, nearly the maximum for her offense, with the sentence upheld last month by an appeals court.
Supporters have voiced concern about how she would be treated in a country that is hostile to the United States and to gay people, and where she has little knowledge of the language.
Russian officials have insisted that it was premature to discuss a prisoner exchange until the legal process in her case had concluded. Her transfer to a penal colony outside Moscow appeared to mark that milestone.
Her lawyers said on Thursday that Ms. Griner had been sent to the IK-2 female penal colony in the small town of Yavas, about 300 miles southeast of Moscow. According to the website of the Russian prison service, the colony can hold 820 inmates.
Former inmates say that harsh conditions, overcrowding, political indoctrination and even brutality are common features of Russian penal colonies.
In 2012, a member of the Russian punk band Pussy Riot said that there had been no hot water, warm clothes or medicine in the penal colony where she and a bandmate were imprisoned, and that people who got sick could die as a result.
Mr. Whelan, 52, the other American whose release has reportedly been sought in a trade for Mr. Bout, has said he has suffered physical abuse and been denied needed medical care while in Russian custody. A former U.S. Marine, he was the director of security and investigations for an American manufacturing company, and had traveled several times to Russia.
After his arrest in 2018 in a Moscow hotel room, the authorities said he had a USB drive containing the identities of employees of a Russian security service. Mr. Whelan’s lawyers say he believed the drive contained photos of churches, and was set up. He was sentenced to 16 years in prison.
Reporting was contributed by Edward Wong, Michael Crowley, James C. McKinley Jr., Ruth Maclean, and Matthew Mpoke Bigg.