More women are lighting up cigarettes around the world even as the smoking rate declines for men, activists attending an anti-smoking conference said Thursday.

About 12 percent of women worldwide smoke, and that figure is expected to rise to 20 percent by 2025, according to a report by the International Network of Women Against Tobacco. The group relied on World Health Organization data.

About 48 percent of men smoke, but that number is expected to decline, according to the report released Thursday at a conference sponsored by the American Cancer Society.

Lorraine Greaves, project leader on the report, said tobacco company marketing is nudging up the female smoking rate in developing countries, much as it did in the U.S. in the 1960s and 1970s.

Greaves, executive director of the British Columbia Centre of Excellence for Women's Health, said billboard ads for cigarettes overseas often show attractive, modern-looking women smoking. Billboard ads are banned in the U.S. under a 1998 agreement between the sates and cigarette makers.

The report said ad campaigns geared toward women overseas have "served to change cultural beliefs about women and smoking," and it cited several countries where such shifts had occurred. For example, it noted that in Turkey, where it used to be "quite unacceptable for a woman to be seen with a cigarette," the rate of smoking among women is now similar to that of men.

Greaves and other women's health advocates noted that a World Health Organization treaty aimed at curtailing tobacco use contains measures designed to cut women's smoking rates, including calling for gender-specific strategies.

The United States has signed but not sent the treaty to the Senate for ratification.

"Where is the good will?" Patricia Lambert, a legal adviser to the South African Ministry of Health asked, referring to the delay.

Also Thursday, World Health Organization officials said they intended to republish and distribute internationally a California study that cited a causal link between second hand smoke and breast cancer.

The U.S. Surgeon general has said there isn't enough evidence to conclude a causal link exists.