LONDON - Nuclear power — long considered environmentally hazardous — is emerging as perhaps the world's most unlikely weapon against climate change with the backing of even some green activists who once campaigned against it.

It has been 13 years since the last new nuclear power plant opened in the United States. But around the world, nations under pressure to reduce the production of climate-warming gases are turning to low-emission nuclear energy as never before. The Obama administration and leading Democrats, in an effort to win greater support for climate change legislation, are eyeing federal tax incentives and loan guarantees to fund a new crop of nuclear power plants across the United States that could eventually help drive down carbon emissions.

From China to Brazil, 53 plants are now under construction worldwide, with Poland, the United Arab Emirates and Indonesia seeking to build their first reactors, according to global watchdog groups and industry associations. The number of plants being built is double the total of just five years ago.