By Alex Kirby
BBC News Online environment correspondent
The only way to meet the UK's promises on tackling climate change may mean it has to opt for nuclear power, the prime minister has told a committee of MPs.
Nuclear memory: Protest is never far away
His declaration will scandalise many environmental groups, but it will draw praise from several influential greens.
Tony Blair made no commitment to build a new round of nuclear power stations, and acknowledged the obstacles ahead.
But he did not mention nuclear energy's inability directly to fuel cars and aircraft, two huge carbon emitters.
Many environmental groups insist we could keep our promises on reducing emissions of the gases scientists say are causing the atmosphere to heat up, without going nuclear.
They say using energy more efficiently, and generating more of it from renewable sources like wind, waves and solar power, would let us make sufficient cuts in the amount of coal, oil and gas we burn.
THE UK & CLIMATE CHANGE
The UK is likely to keep its promise to cut greenhouse gas emissions to 12.5% below 1990 levels by 2010
Ministers say they want to cut carbon dioxide emissions by 20% by 2010, but look unlikely to manage this
Government policy is to cut greenhouse emissions by 60% by 2050
But within the last few weeks two leading figures in the environmental movement have urged a new look at the possible merits of nuclear power.
Professor James Lovelock, who developed the Gaia Hypothesis, said: "We must stop fretting over the minute statistical risks of cancer from chemicals or radiation. Our goal should be the cessation of fossil fuel consumption as quickly as possible."
Days later Sir Crispin Tickell, formerly the UK's ambassador to the United Nations, said British politicians had failed to give a lead on nuclear energy.
He said: "I reproach this government and its predecessor for not putting more effort and resources into coping with the problems of high-level waste. Next I reproach them for fudging nuclear issues.
Level playing field
"The problems of true cost, safety, proliferation, security, risk and the rest should be examined in a complete overall assessment of nuclear against other forms of renewable energy to lay a proper foundation for debate and future policy."
Sir Crispin touched a raw nerve in mentioning nuclear waste. Despite claims that there are solutions - burying the waste in the ocean depths, for example, to be absorbed into the seabed - many nuclear scientists remain unconvinced.
UK ENERGY USE
In 2001 transport used 34% of total energy, and aviation used 21% of transport's share
From 1990 to 2001 aviation's energy consumption rose by 56%, rail's by 8% and road's by 7%
In 2000 domestic demand accounted for 30% of total energy
The industry insists modern reactors are as safe as they can be - and at least as safe as any other large power plant.
But memories of Windscale, Three Mile Island and Chernobyl persist, and persuade many of us that nuclear energy is inherently dangerous.
It is also a tempting target for terrorists, and it would take years for new power stations to be built.
It could eventually buy us some time in moving towards a less polluting society. But at the moment there is little if anything it can do to reduce the burning of oil in land vehicles and aircraft - two main and growing sources of greenhouse gases.
Eventually, one could envisage perhaps nuclear feeding a power network into which everyone plugged their electric cars - but it will not happen tomorrow.
Mr Blair did not suggest he would necessarily be the leader to commit the UK to a nuclear renaissance, saying simply that he had "fought long and hard" to keep the option open.
Understandably, politicians often find themselves echoing St Augustine's fervent but post-dated prayer for a blameless life: "Lord, give me chastity - but not yet."
One day soon, though, a British prime minister will have to decide whether or not we can cut our greenhouse emissions without the help of nuclear power, and face the implications of that decision.