Russia could be willing to discuss a potential prisoner swap with America involving a jailed Wall Street Journal reporter, Evan Gershkovich, but only after his trial on espionage charges, a top Russian diplomat said Thursday.

Mr. Gershkovich, 31, his employer, and the U.S. government all deny he was involved in spying and have demanded his release.

Russia’s deputy foreign minister, Sergei Ryabkov, told the state news agency Tass that talks about a possible exchange could take place through a dedicated channel that Russian and American security agencies established for such purposes.

“We have a working channel that was used in the past to achieve concrete agreements, and these agreements were fulfilled,” Mr. Ryabkov said, adding that there was no need for the involvement of any third country.

He emphasized, though, that Moscow would only negotiate a possible prisoner exchange after a trial. “The issue of exchanging anyone could only be considered after a court delivers its verdict,” he was quoted by Tass as saying.

That practice is in keeping with previous cases in which Russian authorities have insisted on completing the judicial process before considering exchanges. It is not clear how long the investigation could last, but other espionage cases have stretched out for a year or more.

In December, an American basketball star, Brittney Griner, was exchanged for a Russian arms dealer, Viktor Bout, following her trial and conviction on drug possession charges. Ms. Griner had been sentenced to nine years in prison and ended up spending 10 months behind bars.

Another American, a Michigan corporate security executive named Paul Whelan, has been imprisoned in Russia since December 2018 on espionage charges that his family and Washington have called baseless.

During the Griner case, the Kremlin repeatedly urged the United States to use the “special channel” to discuss it and work on a potential prisoner swap, saying such private communications were the only appropriate means for resolution, rather than public statements and speculation.

Mr. Gershkovich could face up to 20 years in prison if convicted. Russian lawyers have said past investigations into espionage cases took a year to 18 months, during which time the suspect could have little contact with the outside world. A Moscow court has received a defense appeal of his arrest that is scheduled to be considered April 18.

Speaking at a panel discussion on the case Wednesday at Columbia University in New York, the newspaper’s chief news editor, Elena Cherney, said the Journal’s lawyers had visited Mr. Gershkovich three times, that he appears to be in good spirits and health, and that he had received updates on one of his favorite soccer teams, Arsenal.

Secretary Blinken urged his Russian counterpart, Sergey Lavrov, this month to immediately secure the release of Messrs. Gershkovich and Whelan. President Biden spoke to Mr. Greshkovich’s parents Tuesday and again condemned his detention. “We’re making it real clear that it’s totally illegal what’s happening, and we declared it so,” he said.

On Monday, Washington declared Mr. Gershkovich as “wrongfully detained,” a designation that means that a particular state department office takes the lead on seeking his release.

On Thursday the special presidential envoy for hostage affairs, Roger Carstens, told NPR, “We will bring Paul Whelan and Evan Gershkovich home.” 

Mr. Carstens, a Trump appointee, said, “In the 26 months of the Biden administration, we’ve brought back 26 Americans.”

It won’t be easy, though. On Thursday, the Kremlin spokesman, Dmitry Peskov, again emphasized Moscow’s claim that Mr. Gershkovich was caught red-handed. He denied reports that President Putin had personally sanctioned Mr. Gershkovich’s arrest.

“It’s not the president’s prerogative. It’s up to the special services, who are doing their job,” Mr. Peskov said in a conference call with reporters.

Russia’s Federal Security Service, or FSB, arrested Mr. Gershkovich at Yekaterinburg, Russia’s fourth-largest city, on March 29. He is the first U.S. correspondent since the Cold War to be detained in Russia for alleged spying.

The FSB, a successor agency to the Soviet-era KGB, accused the young reporter of trying to obtain classified information about a Russian arms factory.

Washington has pressed Russian authorities to grant U.S. consular access to Mr. Gershkovich. Russia’s foreign ministry spokeswoman, Maria Zakharova, said Wednesday that Moscow would provide it “in due time in line with the consular practices and Russian legislation.”

Mr. Gershkovich is being held at Moscow’s Lefortovo prison, which dates from the tsarist era and has been a terrifying symbol of repression since Soviet times. Mr. Whelan was also held in Lefortovo until he was sent to another prison to serve his 16-year sentence after his conviction in 2020.

The Wall Street Journal launched a campaign to support Mr. Gershkovich, offering the public a way to submit letters to him via its website. Members of the Journal’s newsroom posted photos of themselves wearing T-shirts that read #IStandWithEvan.

“We need to make sure that Evan and his wrongful detention and the effort to get him back remain in the public consciousness and don’t fade with the news cycle,” Ms. Cherney said in explaining the campaign’s goal at Wednesday’s event at Columbia.

“What we’re doing is trying to ensure that we do reach Evan with these messages,” she added. “We do what we can to keep his spirits up, as well.”