Blair has signalled a willingness to consider sanctioning new nuclear reactors to cut carbon dioxide emissions but he faces opposition from environmentalists and parts of his Labour Party.

"We have to make decisions very quickly and I think the important thing here is to give the green light to the private sector utilities to give them nuclear as an option," King told BBC Television.

All but one of the UK's nuclear power stations are due to close by 2023. The government is due to publish new plans on how to curb the country's use of electricity and fuel in 2006.

But Environment Minister Margaret Beckett said nuclear power raised problems of cost and waste disposal, although she rejected suggestions she was "anti-nuclear".

"I've always accepted ... that particularly because of climate change, we could come to a position where we and other governments were driven back towards nuclear ... We can't afford to close the door on nuclear," she told the BBC.

The decline in nuclear power was jeopardising efforts to cut greenhouse gas emissions, King said. Nuclear power will contribute four percent of Britain's energy needs by 2010 without new reactors, from 21 percent now, he added.

VOLUNTARY EMISSIONS TARGETS

But Beckett said any move on nuclear power would not help Britain meet short-term emissions targets.

Projections show Britain will miss its domestic target of cutting CO2 emissions by 20 percent compared to 1990 levels by 2010, although it is on track to meet obligations under the international Kyoto protocol.

Blair has put climate change at the heart of Britain's presidency of the Group of Eight rich nations this year but environmentalists have accused him of rowing back on emissions targets after he recently called for a "more sensitive" set of mechanisms going forward.

The UN meeting in Montreal from Nov. 28-Dec 9 will look at ways to widen Kyoto to non-participants including the United States and developing nations like China and India after 2012.

King said Blair still believed developed countries should follow mandatory Kyoto targets but said Britain would press developing countries outside Kyoto to adopt voluntary targets.

"We believe absolutely that the targets set and fixed in Kyoto are targets the developed world ought to be following, he said. "India, China, Brazil, South Africa and Mexico, what we are saying to those countries is come and join the discussions and we are not telling you in advance that you are facing targets."

Environmentalists say voluntary targets are not worth the paper they are written on.