India, June 3 -- The hall where Sergey Ryabkov was speaking on Wednesday morning was not short on economic ambition. Finance ministers and energy executives had filled the corridors of the St. Petersburg International Economic Forum since dawn, debating commodity flows and sanctions architectures. But Russia's Deputy Foreign Minister kept returning to a subject that had nothing to do with trade: a hole in a turbine building beside a reactor on the Dnieper.

The Zaporizhzhia Nuclear Power Plant is now the principal preoccupation of Russia's Foreign Ministry, Ryabkov told reporters on the forum's sidelines. "Our main concern now is for the ZNPP," he said Wednesday, adding that the ministry is "very closely involved" and that the entire Rus...