from Barry Wigmore in New York

Last updated at 07:38 12 June 2006

Doctors will this week declare war on America's soft drinks industry by calling for a 'fat tax' to combat the nation's obesity epidemic.

Delegates at the powerful American Medical Association's annual conference will demand a levy on the sweeteners put in sugary drinks to pay for a massive public health education campaign.

They will also call for the amount of salt added to burgers and processed foods to be halved.

The moves come as U.S. doctors - like their British counterparts - are becoming increasingly alarmed at the growing number of deaths linked to obesity.

The resolution will put doctors on a collision course with Coca-Cola and Pepsi, plus the likes of McDonald's and Burger King.

Sales of soft drinks in U.S. schools are in decline ahead of the introduction of guidelines allowing only healthier low-calorie drinks, plus milk and certain fruit juices, over the next two years.

But the medical association wants to go further. Delegates at its Chicago conference are gunning in particular for high fructose corn syrup, the sweetener which is added to everything from ketchup to cola.

One American politician labelled it the 'crack of sweeteners' because it is so widespread.

Some U.S. cities and states already levy taxes on soft drinks or junk foods that raise £500million a year, said Michael Jacobsen, director of the Centre for Science and the Public Interest, an independent health watchdog. But earmarking tax revenue for programmes promoting better diet would be a first, he added.

American doctors are seeing the same alarming trends as those in Britain where obesity is considered to be a 'ticking timebomb of epidemic proportions'.

More than 30,000 Britons die each year because of obesity. In England, 47 per cent of men and 33 per cent of women are overweight, with around a fifth being obese. The problem costs the Health Service £500million in consultations, drugs and other therapies.

Life insurance companies are considering increased premiums for overweight clients because so many are dying prematurely from heart disease and cancer. Cancer Research UK has warned that obesity will soon cause more cancers than smoking.

Just as alarming is the rapid growth in childhood obesity. Among six-year-olds, one in ten is classed as obese, rising to one in five among 15-year-olds.

The Government has warned that the current generation of schoolchildren could be the first to live shorter lives than their parents.