GENEVA — Tobacco use kills almost 5 million people a year worldwide and the toll could double within 20 years, the head of the U.N. health agency said Friday.

In comments ahead of the annual World No Tobacco Day on Monday, Lee Jong-wook said most tobacco-related deaths occur in developing countries, placing a huge burden on health services that cannot afford the extra costs.

For example, the director-general of the World Health Organization noted that the annual cost of treating tobacco-related diseases in Egypt is an estimated $546 million.

"The world cannot accept such easily preventable human and economic losses," Lee said.

The number of tobacco users is now 1.3 billion, but that is expected to increase to 1.7 billion in 2025, WHO said.

"Consumption is inversely related to the socio-economic level — it goes up as the standard of living goes down," Lee said.

"I urge everyone to think of how we can help to break the vicious circle of the poor consuming tobacco more, and tobacco consumption increasing poverty."

Tobacco also can damage countries' economies through increased health-care costs; the loss of foreign exchange, since most countries are net tobacco importers; the loss of tax revenues because of smuggling; and the environmental damage from tobacco cultivation.

Many governments organize events May 31 to commemorate World No Tobacco Day, meant to spotlight the fight against smoking-related illnesses.

Lee urged more countries to sign WHO's landmark anti-tobacco treaty, which aims to direct policies to reduce the health and economic damage of tobacco. WHO concluded the treaty in May 2003.