Secretary of State Antony Blinken and Russian Foreign Minister Sergei Lavrov spoke by phone on Friday about a U.S. proposal to secure the release of WNBA star Brittney Griner and fellow jailed American Paul Whelan.

Blinken said he “pressed the Kremlin to accept” the offer during what he described as a “frank and direct conversation.”

“I urged Foreign Minister Lavrov to move forward with that proposal,” Blinken said. “I’m not going to characterize his response and I’m not going to give you an assessment of whether I think things are any more or less likely, but I think it was important he hear directly from me on that.”

President Biden reportedly has signed off on a 2-for-1 prisoner exchange that would secure the release of Griner and Whelan. In return, the U.S. would relinquish notorious Russian arms trafficker Viktor Bout, who is serving a 25-year sentence in an Illinois prison for conspiring to kill Americans and sell weapons to terrorists.

Russian officials were also tight-lipped about whether any progress was made during the call between Blinken and Lavrov. In a statement chiding the U.S. for negotiating through the media before an agreement had been reached, the Russian Foreign Ministry said Lavrov “strongly suggested” to Blinken that he return to “quiet diplomacy.”

The conversation between Blinken and Lavrov was their first since Russia invaded Ukraine and the U.S. responded by imposing unprecedented economic sanctions. Relations between the two former Cold War adversaries had been so icy that earlier this month Blinken reportedly boycotted a group photo at a diplomatic summit in Bali because he didn’t want to pose alongside Lavrov.

On Friday, a CNN report possibly shed light on why no deal has been struck for Griner and Whelan despite the U.S. offering Bout weeks ago. The network reported that Russia had informally requested through back channels to add convicted murderer Vadim Krasikov to the proposed swap.

The U.S. apparently didn’t take the counteroffer too seriously considering Krasikov is serving a life sentence in Germany after the murder of a former Chechen fighter in Berlin. In a statement in response to the CNN story, National Security Council spokesperson Adrienne Watson said that Russia’s attempt to include Krasikov in the exchange was “a bad faith attempt to avoid the deal on the table that Russia should take.”

Russian officials have previously said they won’t accept any deal until the conclusion of Griner’s drug trial. Griner’s attorney, Maria Blagovolina, told Yahoo Sports on Thursday that she expects a verdict and sentencing to occur during the first half of August.

Griner has been behind bars since Feb. 17 when she flew into a Moscow airport and Russian customs officials allegedly found vape cartridges containing hashish oil in her luggage. She has been charged with possession of an illegal drug and drug smuggling and could receive a prison sentence of up to 10 years if convicted.

In early May, the State Department classified Griner as wrongfully detained without explanation and began working to negotiate her release. Whelan, a former Marine, is currently serving a 16-year sentence for espionage charges that he has consistently denied and that the State Department has described as bogus.

Experts who spoke to Yahoo Sports on Thursday are skeptical that a deal exchanging Bout for Griner and Whelan is imminent. Dartmouth University foreign policy fellow Danielle Gilbert contends that the U.S. wouldn’t have publicly revealed its offer if it thought Russia was poised to accept.

“My hunch is that this is not going to be the final deal,” Gilbert said. "The fact that the administration is announcing they put this on the table and the Russians didn't agree to it makes it feel like we're a few steps away from this being completed."