U.S. Secretary of State Antony Blinken spoke by telephone Friday with Russian Foreign Minister Sergey Lavrov, pressing him to accept a U.S. proposal to secure the release of American professional basketball star Brittney Griner and former U.S. Marine Paul Whelan.

The call is the first conversation between the two top diplomats since Russia’s invasion of Ukraine in late February and the highest-level known contact between the two countries since that time.

“We had a frank and direct conversation,” Blinken told reporters Friday at the State Department.

“I pressed the Kremlin to accept the substantial proposal that we put forth on the release of Paul Whelan and Brittney Griner,” he said.

A Russian Foreign Ministry statement did not say whether the two sides had made any headway but chastised the United States for not pursuing “quiet diplomacy.”

“Regarding the possible exchange of imprisoned Russian and U.S. citizens, the Russian side strongly suggested a return to the practice of handling this in a professional way and using ‘quiet diplomacy’ rather than throwing out speculative information,” the statement said.

FILE - Americans Paul Whelan and Brittney Griner, both detained in Russia, are seen in a combination photo.

FILE – Americans Paul Whelan and Brittney Griner, both detained in Russia, are seen in a combination photo.

The United States announced this week that it made an offer to Russia for a prisoner swap back in June but nothing has yet come of it.

U.S. government officials describe the proposed terms of the swap as sending convicted Russian arms trafficker Viktor Bout back to Moscow in exchange for the release of Americans Griner and Whelan.

CNN reported Friday that Russia has requested that another Russian prisoner be added to the swap. The news agency cited multiple sources familiar with the discussions as saying Russia requested the inclusion of Vadim Krasikov, a former colonel from the country’s domestic spy agency who was convicted of murder in Germany last year.

News of a possible prisoner swap came as Griner, who has admitted arriving in Russia in February with vape canisters containing cannabis oil in her luggage, testified at a court hearing Wednesday that a language interpreter provided to her translated only a fraction of what was being said as authorities arrested her.

Griner, who faces up to 10 years in prison if convicted of transporting drugs, said she was instructed by officials to sign documents at the Moscow airport without them providing an explanation for what she was acknowledging. A Russian court has authorized her detention until December 20.

Whelan, a former U.S. Marine, has been imprisoned in Russia since 2018, accused of espionage. His family and Griner’s have been pleading with the White House to expedite efforts to gain their release.

Russia for years has sought the release of Bout, an arms dealer once labeled the “Merchant of Death.” He was sentenced to 25 years in prison in 2012 after his conviction in a scheme to illegally sell millions of dollars in weapons.

The possible prisoner swap was approved by U.S. President Joe Biden, CNN reported, with Biden’s support overriding opposition from the Department of Justice, which is generally against prisoner trades for fear they would incentivize other governments to seize Americans overseas in hopes of prisoner swap deals of their own.

The U.S. secured the release from Russia of American Trevor Reed in April. He was a former Marine who was held captive in Russia for more than two years after being accused of assaulting a Russian police officer. He was traded for Konstantin Yaroshenko, a Russian pilot then serving a 20-year federal prison sentence for a cocaine smuggling conspiracy.

Some information in this report came from The Associated Press and Reuters.