LONDON — American utility companies are returning to the idea of building nuclear power stations. They believe they can get approval for licenses to start doing so by 2007, and they also believe, despite bitter past experience, that safety problems can finally be solved and the economics can be justified.

This is bold thinking, but is it realistic? All over the world nuclear power programs have long been in limbo for years and a huge political resistance has developed. Although accidents have been rare and performance generally reliable, America’s Three Mile Island incident in 1979 and, even more, the Soviet Union’s Chernobyl disaster in 1986 have left an indelible imprint of fear that no amount of statistics showing years of safe operation seem able eradicate.

An even deeper fear focuses on the handling of radioactive waste. The public remains convinced that the super-toxic material left over from nuclear electricity generation cannot be transported, stored or disposed of safely.

In vain the nuclear industry has pointed out that the quantities involved are minute (all the waste ever generated by nuclear power stations so far would probably cover no more than three football fields) and that poisonous radioactive material can be encased in glass (vitrified) and buried for centuries until it is harmless. But the public remains skeptical.

Then there is the cost problem. The issue that has long frightened investors away from the nuclear power industry is the colossal cost of eventually decommissioning a plant. It is what made nuclear power so unattractive to financial markets in Britain back in the 1980s when the rest of the electricity industry was successfully privatized.

These are still formidably steep mountains to climb, so why the revived optimism? The answer is that nuclear advocates now think that new designs and technical innovation can overcome safety as well as cost problems. They argue that the danger of a nuclear reactor core being drained of coolant and overheating, as happened at Chernobyl (and as depicted in the mythical but chilling movie “The China Syndrome”), can be eliminated with new designs.

They also maintain that decommissioning costs can be drastically cut and that electricity can be generated from new nuclear stations for about $1.70 a kilowatt-hour over the reactor’s lifetime, compared with $1.80 for coal-fired stations and much more for oil and gas.

But much more significant than any of these semi-technical issues are two new “drivers” that nuclear enthusiasts point to. The first is, quite simply, that nuclear power is clean — it produces no carbon dioxide (CO2 emissions. Of course, the process of constructing a nuclear power station, with its megatons of concrete and metal, is highly energy-intensive. But once the plant is up and running, it is goodbye to the CO2 pollution that many fear is threatening the planet.

The second big new “driver” for the cause of nuclear energy is that oil and gas supplies are becoming less and less reliable. There may be plenty of oil and gas left, both in discovered reserves and in hidden, more remote areas (such as under the Arctic ice cap). But at what cost can it be extracted and will it keep flowing? Those are the questions.

More and more hydrocarbon energy deposits are destined to come from regions that are very unreliable politically. How painful will the price of a barrel of oil get to cover the vast risks of interruption, sabotage, terrorism, blackmail, insurgency, revolution — not to mention natural disasters like earthquakes?

Can countries afford to rely on the boiling Middle East, unsettled Nigeria, unpredictable Russia, troubled Venezuela, embattled Algeria, for example, for their daily light, heat and industrial production?

Nations and societies that are self-sufficient in oil can perhaps sleep a little easier in face of all these dangers. But America has long ceased to be one of these. Since claiming self-reliance in energy 40 years ago, it has allowed itself, almost absentmindedly, to drift into the hair-raising position of having to import 73 percent of its daily oil needs from the outside world.

Of course, what goes for America goes for other countries, too, but at least some of them are getting prepared. Japan has made strides toward using less oil and is thinking, however reluctantly, about expanding nuclear power further.

Finland, always a center of green issue concerns, has bitten the bullet and is building six new, state-of-the-art, nuclear stations. Even Germany is overcoming its long-held hesitations.

Admittedly the wider dangers of nuclear power in an age of terrorism cannot be overlooked. The tightest possible international monitoring of all nuclear activity is essential if nuclear materials are not to slip into irresponsible hands.

But the plain truth of the world’s energy future is now written in letters a mile high: Burning fossil fuels has become both a high risk and threat to the planet.

Renewable energy can help at the margin, but even giant wind farms have a big environmental downside. Conservation and solar panels can do their part, especially in the home, but the massive power that industry and 21st-century life need will have to come increasingly from safe nuclear energy. The experts know this as do the technicians, but dare the politicians break the news to a still nervous public, or will they wait until the lights go out, industry seizes up and the heating fails — by which time it will be too late to take remedial action.

As President George W. Bush settles into his third term, his advisers are rightly warning him that America needs a radically new energy policy. Could this be the time for some real leadership?

David Howell is a former British Cabinet minister and former chairman of the Commons Foreign Affairs Committee. He is now a member of the House of Lords.