Britain is backing the treaty, which will bring in international regulations on tobacco advertising and places where smoking is allowed, and will attempt to raise cigarette taxation in all countries. The treaty, which will be binding on signatories, should be in place by 2002 or 2003, said Dr Brundtland, a former Norwegian prime minister, yesterday.
It was necessary, she said at a London conference on environment and health, to deal with the "mounting epidemic" of smoking, particularly in the developing world.
The treaty was being negotiated by all 191 WHO member states - in effect the entire membership of the United Nations. It was likely to be the world's first binding treaty on human social behaviour.
The embryo agreement, formerly entitled the Framework Convention on Tobacco Control, is very much the personal project of Dr Brundtland, who became head of the WHO last year after a hugely influential career on the world diplomatic stage. The Brundtland Report, her 1987 investigation of environment and development problems, led directly to the 1992 Earth Summit in Rio do Janeiro.
The idea of a world cigarette smoking agreement has been canvassed before in the organisation, but Dr Brundtland has now given it priority.
Yesterday, she said many countries were backing it, including the United States, as well as Britain, although some tobacco-growing states in the developing world feared that their economies would suffer if consumption dropped.
But it was likely to continue at a high level, said Dr Brundtland. The purpose of the treaty was to halt the rate of increase of smoking. "We are saying that this is a product which is not safe and needs to be regulated. There is a direct parallel with control of environmental hazards or food security."
Tessa Jowell, the Minister for Public Health and architect of the Government's White Paper Smoking Kills, said at the conference: "In an increasingly global world, where national boundaries are unable to stop the communication of pro-tobacco messages, it is essential that we reinforce international co-operation to tackle tobacco."
Dr Brundtland later released a new WHO study, saying that almost half the world's children - 700 million of them - are exposed to the tobacco smoke of adults.
Passive smoking is "a real and substantial threat" to child health, the study says, causing death and suffering from bronchitis, asthma and pneumonia, as well as contributing to heart disease in later life.
The study calls for legislation to protect children from cigarette smoke in public places such as schools, nurseries and leisure facilities.
r Kevin Barron, a British Labour MP and anti-smoking campaigner, has protested over loopholes in tough new controls to be announced today by the Government on tobacco sponsorship of international snooker and advertising on clothes and other goods. Snooker may now escape a ban until 2006, as will Formula One motor racing.