Ontario also said it intends to double the production of renewable energy -- hydro, wind, solar and bio-energy -- to 15,700 megawatts a year by 2025, and boost conservation efforts to cut energy use by some 6,300 megawatts a year.

Election promises to close polluting coal-fired power stations will be delayed because the energy-hungry province still needs the power they generate.

"We believe this plan will provide Ontario with stable, reliable, affordable, competitive electricity," Ontario Energy Minister Dwight Duncan told a news conference.

"The only way to manage price and to keep our prices competitive is to increase supply and or decrease demand, and we are doing both."

Ontario originally planned to phase out its coal-fired generating stations by the end of 2007 to cut air pollution and greenhouse gas emissions, although that deadline had already slipped.

The proposals meet some of the demands of a report from government-owned electricity producer Ontario Power Generation that suggested half Ontario's electricity be produced by nuclear reactors within 20 years. At present, about 30 percent of OPG's capacity of 22,173 megawatts is from nuclear plants.

Ontario ordered OPG to begin an environmental assessment of new nuclear plants and start feasibility studies on refurbishing existing facilities.

But Duncan said Ontario would limit nuclear capacity to current levels of around 14,000 megawatts.

The pro-nuclear announcement prompted an angry reaction from environment group Greenpeace, whose members occupied Duncan's office to try to get Ontario to withdraw the plan.

"This is one of the biggest nuclear programs proposed anywhere in the world since the 1970s...we have to draw a line in the sand," said Greenpeace activist Dave Martin.

Duncan said it could take up to two years to find a builder for new nuclear reactors and said he had held informal talks with several firms, including Atomic Energy of Canada Ltd., General Electric , Areva , and Westinghouse Electric Co., which is being taken over by Toshiba Corp.

"It is our preference to use Canadian companies and technology, but our first responsibility is to the people of Ontario. We must ensure that we are providing the best technology at the best price."