U.N. nuclear watchdog chief Rafael Grossi said Tuesday there is no direct safety issue from Ukrainian staff being barred from accessing the Russian-occupied Zaporizhzhia nuclear power plant, which Ukraine has called a "grave concern."

"The situation is not sustainable in the long term. At the same time, in the present configuration in shutdown, the staff that is there can do the job," International Atomic Energy Agency (IAEA) chief Grossi said in an interview with Reuters.

He responded: "Not directly" when asked whether there were any safety issues arising from the staff who are banned from the plant.

The Zaporizhzhia nuclear power plant, formerly controlled by Ukrainian state-owned company Energoatom, was seized by Russian forces during its invasion of Ukraine two years ago and continues to be on the frontline of the war.

Last week, the IAEA's Board of Governors voted to demand Russia withdraw from the plant and that it be returned to the control of Ukrainian authorities.

Although some Ukrainian staff currently work alongside Russians to operate the plant, some Ukrainians have been barred from the plant for refusing to sign new Russian contracts.

Grossi has put the number of holdouts at around 100. Ukrainian Energy Minister German Galushchenko has said that was "another Russian lie" and the real number was 380, adding that the lack of staffing meant the situation was "moving to (a) nuclear accident."

"This is a matter of a bit of subjectivity," Grossi said Tuesday when explaining the discrepancy of the numbers.

The comments came after Grossi met with Russian President Vladimir Putin on Wednesday to discuss the Zaporizhzhia nuclear power plant, among other issues.

Grossi said Putin confirmed his cooperation in ensuring the safety of the plant during their talks.

The IAEA gave a technical assessment of the current situation at the Zaporizhzhia plant and discussed potential future plans for restarting it given its current condition, Grossi said, without elaborating on further details.