Prime Minister Yoshihiko Noda says Japan has no choice but to restart its idled nuclear reactors by the middle of next year in spite of growing public opposition to nuclear power.

More than 20,000 people marched in Tokyo this week to demand an early end to the use of nuclear power.

But Mr. Noda told the Wall Street Journal in an interview Tuesday it is “impossible” for Japan to get by without the plants, most of which have been shut down since the catastrophic accident at the Fukushima nuclear power plant after the March earthquake and tsunami.

He said Japan cannot afford to let the plants remain closed because a shortage of power will damage Japan's overall economy.

Power shortages have slowed Japan's return to full production since the March disaster, with tough energy conservation measures imposed on homes, offices and factories. Japan on Wednesday announced a larger-than-expected trade deficit, driven in part by record imports of natural gas to replace lost nuclear power generation.

Mr. Noda and his predecessor, Naoto Kan, both have spoken in favor of gradually phasing out of nuclear power. But Mr. Noda, who took office on September 2, told the Wall Street Journal he is unsure whether it can be eliminated completely.

Mr. Noda also said he would not allow the task of earthquake reconstruction to stand in the way of addressing Japan's economic problems. He said his biggest task is to balance economic growth and fiscal reform.