By Nick Triggle BBC News health reporter

Some 1.8bn people smoke around the world

By 2020 the mortality rate will have doubled - the equivalent of 10 million a year.

To tackle the rise, which is expected to be felt hardest in developing countries, the World Health Organization's tobacco control treaty comes into force on Sunday.

It is regarded as smoking's answer to the Kyoto agreement - only with teeth.

Ratified by 57 countries, including the UK, the document sets out a programme to reduce the number of people smoking across the world.

Under its terms governments have promised to introduce smoking bans, tobacco advertising restrictions and health warnings on cigarette packets, draw up anti-smuggling strategies and agree to increase tax on tobacco sales.

Developing countries

It has been hailed as a landmark in the fight against smoking after developing countries - where 84% of the world's 1.8 billion smokers live - took a lead role in setting it up.

Two thirds of the 57 founding members are developing nations.

And while many of the Western governments which are on board have already taken a tough stance against smoking, the signatories do include Japan and Germany, both of which have been slow to introduce tobacco control.

Supporters also point out some of the world's largest tobacco growers - India, Japan, Pakistan, Thailand and Turkey - have agreed to be bound by it.

Key requirements of treaty Ban tobacco advertising, sponsorship and promotion, where constitutions allow, within five years Tobacco packaging must include health warnings covering at least 30% of packet within 3 years Introduce measures to protect people from second-hand tobacco smoke in public places Draw up strategies to combat smuggling Adopt tax policies which discourage smoking

But with just over a third of the WHO's member states adopting the treaty, the impact is likely to be limited initially.

Dr Vera Luiza Da Costa e Silva, director of the Tobacco Free Initiative, the WHO department behind the treaty, said she expected the number of countries to have ratified it to top 100 by November.

More than 100 other countries have also signed the treaty, but will not be bound by its restrictions until they agree to ratify it.

"Obviously getting other countries to ratify it is the natural step and I think that will happen.

"The framework allows member countries to work together to protect themselves from the big cigarette manufacturers through tightening marketing restrictions, controlling pricing and sponsorship.

"This is particularly relevant for the developing countries, which are increasingly being targeted by tobacco companies."

Smoking bans

But she said it was also relevant to countries who had already introduced advertising and smoking bans.

"The framework also deals with smuggling, that is a problem for these countries."

Global tobacco control expert Jeff Collin, of the London School of Hygiene and Tropical Medicine, also believes the treaty, called the Framework Convention on Tobacco Control, will have an impact.

"This is a very strong treaty that asks a lot of signatories, unlike say Kyoto. There would be no point in having a weakened treaty that was acceptable to everyone.

"What has been particularly impressive is that the developing countries from Africa and Asia have led the way, they really wanted this.

India, a leading tobacco growing country, has ratified the treaty

"It has had a low profile as many think it will only have an impact in developing countries but that is not true.

"It also encourages best practice, new protocols and further progress, some of the western countries could really take a lead.

"And you only need to have a look at the tobacco industry's sponsorship of Formula One.

"They can get round national bans because TV shows the advertising when the races happen in countries with no ban."

Anti-smoking campaigners also believe the treaty will have an impact.

Deborah Arnott, director of Ash, said: "The smoking industry is very nervous about it, it is already encouraging countries to adopt policies to cut smoking such as public bans and warnings.

"We are not going to see it make an impact straight away but over a number of years I think we will see a difference."

She also believes it could force the UK government into a rethink about its proposed smoking ban which does not include pubs which do not serve food.

"I think you could argue the public are not being protected."

Warnings

But the apparent lack of enthusiasm among EU states has caused some concern.

Only 10 of the EU's 25 states have ratified the treaty even though under European legislation health warnings are placed on all cigarette packets and a total ban on advertising in print and on-line comes into force in July.

Philip Tod, a spokesman on health and consumer protection at the European Commission, agreed the remaining 15 member states should commit themselves.

"The treaty is an important step forward in tackling tobacco control worldwide but we need more countries to sign up.

"The framework is a reflection of EU actions on tobacco control so we would expect member states to ratify it."

We sell our products in more than 160 countries and in all of them we target adults and support regulation of the industry Di Giovanni Tommaso, of Philip Morris

However, some believe the treaty is weakened by the refusal of the US to become a member.

Officials close to the treaty negotiators told BBC News that ever since the idea was first proposed in 1995, the US has been trying to water down the contents under pressure from the tobacco industry.

Laurent Huber, a co-ordinator for the Framework Convention Alliance, an international umbrella group to support NGOs in implementing the treaty, said: "If there is one area of it that is weak, it is to do with trade.

"A lot is expected on public health, but I am afraid it is not as strong on trade.

"And that is where the battle is going to be. The tobacco industry is increasingly looking to push its trade into poorer countries."

And he said that as the US - home to many of the leading cigarette manufacturers - had not ratified the treaty, the tobacco industry could exploit loopholes to push their interests abroad.

Behind the scenes the tobacco industry is said to have objected to many of the treaty measures, however in public market leaders say they are behind it.

Di Giovanni Tommaso, a spokesman for Philip Morris, the world's largest cigarette manufacturer, said: "We look forward to continuing to work with governments on making sure different regulatory systems complement each other.

"We sell our products in more than 160 countries and in all of them we target adults and support regulation of the industry."