The World Conference on Tobacco or Health is meeting in Chicago on Tuesday for a special session on plans for an international tobacco control convention.

Drafting of the treaty will start in October on a series of measures designed to promote a united anti-smoking front.

Many of the most widely used policies to curb tobacco use can be completely undermined if countries adopt them individually.

The scheme, backed by the World Health Organisation is seen as the only way in which countries, faced with the international scope of the big tobacco companies, can cut rates of smoking-related diseases.

Officials say putting up the price of tobacco products does not work if vast quantities of cheaper cigarettes are immediately smuggled in.

Bans or restrictions on tobacco advertising are also useless if the banned advertisements can be seen on satellite television, or in imported magazines.

Liberalisation of trade under international treaties is also a problem as countries open their markets to international tobacco companies with far more aggressive marketing tactics than their local counterparts.

US support

The plans for this treaty however have one big advantage - an unusual degree of support from the United States, which has traditionally remained unenthusiastic about such projects.

On Monday, the American health secretary, Donna Shalala, told the meeting in Chicago that she had been urged by President Clinton to negotiate a very strong position.

However, the US Government is keener on some parts of the convention than others.

They want to emphasise the protection of children and young people, which are seen as electoral vote-winners, but stop short of a complete ban on advertising, fearing objections from the powerful tobacco industry.

This week's discussions in Chicago are clearly only the beginning of what could be a long process.