White House national security spokesman John Kirby reiterated calls to create a demilitarized zone around the facility, which was occupied by Russian troops in the early weeks of the six-month-old war and has experienced close hits by rockets or artillery shells.

"As we've said many times, a nuclear power plant is not the appropriate location for combat operations," Kirby told reporters.

He said the risks of keeping the plant going grew last week when fires in the area forced the shutdown of a diesel-fueled electric plant that provides backup power to the Zaporizhzhia plant, potentially threatening nuclear reactor operations.

"We continue to believe that a controlled shutdown of the Zaporizhzhia nuclear reactors would be the safest and least risky option in the near term," Kirby said.

He also offered strong support for the looming visit to Zaporizhzhia by inspectors of the International Atomic Energy Agency as he warned of a potential nuclear disaster at the plant due to the war.

"Russia should ensure safe, unfettered access for these independent inspectors," Kirby said.