A Moscow court next week will hear an appeal by Gershkovich's legal team against a ruling that he be held in pre-trial detention at Moscow's Lefortovo prison until at least May 29.
The 68-year-old convicted spy Jonathan Pollard says he has moved on from his decades in US prison and is now living in Israel.
Russia has presented no evidence to support the case against Gershkovich, which is proceeding in secret.
The Post has indications that the conclusions of the leaked US intelligence that the Mossad aided judicial reform protests is wrong either as disinformation or confusion.
The Kremlin said Gershkovich had been carrying out espionage "under the cover" of journalism.
Russian spy Sergey Vladimirovich Cherkasov operated for a decade under a Brazilian alias and targeted the US and ICC in The Hague. However, he also gathered information on Israeli figures.
The Russian security services said in a statement it had opened a criminal case against Evan Gershkovich for suspected espionage.
According to prosecutors, the suspect "acted for the benefit of Russian intelligence by obtaining and collecting information... on critical infrastructure."
Tehran detained seven French nationals in what Paris has said are arbitrary arrests that are akin to state hostage-taking.
Ayat Abdullah and another man, Abed Al-Rahman, were recruited and paid to observe and report on IDF troops along the Syrian border.