BRUSSELS — The German chancellor, Angela Merkel, is pushing for the European Union to conduct “stress tests” on all the nuclear reactors of its member countries in the wake of Japan’s calamity.

Critics of the proposal want to know whether it is a political maneuver, or whether there are real safety issues with the 143 power reactors now operating throughout the bloc.

Mrs. Merkel plans to meet with other European Union heads of state and government on Thursday to discuss what they should do to ensure the safety of the reactors on European soil — a bigger fleet than the 100 or so operating in the United States.

By agreeing to the tests, European leaders would take a “fundamental” step to ensure the future of nuclear power in Europe, Luis Echávarri, director general of the Organization for Economic Cooperation and Development’s Nuclear Energy Agency, said during an interview Wednesday.