The Wall Street Journal reporter was arrested on charges of espionage, a charge that both Mr. Gershkovich, the US, and the Wall Street Journal vehemently deny. Despite the denial, Mr. Gershkovich has now spent over 250 days in prison.

During a news briefing on Tuesday, US state department spokesperson Matthew Miller revealed that Moscow had rejected a "substantial" offer made by the US to secure the release of Mr. Gershkovich and fellow US detainee Paul Whelan. Mr. Miller did not provide further details on the specifics of the offer.

The disappearance of Evan Gershkovich occurred after he lost contact with his editors while working in Yekaterinburg, located 1,600km (1,000 miles) east of Moscow, on March 28. US officials reported that Mr. Gershkovich's driver dropped him off at a restaurant and, two hours later, his phone was turned off. The newspaper was unable to locate him within the city.

Russia's Federal Security Service (FSB) claimed that Mr. Gershkovich was engaged in "illegal activities" and alleged that he had collected classified information related to the Russian defense industry while "acting on US instructions". The Wall Street Journal has openly refuted these claims.

To mark Mr. Gershkovich's 250th day of detention, the editor and publisher of the Wall Street Journal released a statement demanding his release from prison. Reporters Without Borders revealed that Mr. Gershkovich was covering the Russian mercenary group Wagner in Yekaterinburg at the time of his arrest.

Mr. Gershkovich has been held in Moscow's Lefortovo Prison, a notorious detention center previously operated by the KGB. Last week, a court extended his detention period until January 30 next year.

Russian officials previously indicated that they might consider a prisoner swap for Mr. Gershkovich, but only after a verdict is delivered in his case. Similar agreements have led to the release of other Americans, including basketball star Britney Griner. However, experts anticipate that the process in Mr. Gershkovich's case could take over a year.

In addition to Mr. Gershkovich, another detainee, Paul Whelan, a US-Canadian-UK-Irish joint citizen, is serving a 16-year sentence for espionage. Mr. Whelan is being held in Mordovia, a region in far southeast Moscow known for its harsh prison conditions. It was anticipated that Mr. Whelan would be released under the same agreement as Ms. Griner, but so far, he remains in custody. The US has declared Mr. Whelan's imprisonment to be politically motivated.

The rejection of the US proposal to secure the release of Evan Gershkovich is a setback in the ongoing efforts to bring him back to the United States. The case highlights the strained relationship between the two countries and the challenges faced by journalists working in regions where tensions run high.