BEIJING - If all goes according to plan, this fall a girl somewhere in China's Yunnan province will tell her boyfriend she can't have sex with him. And he'll have an abstinence program from the United States to thank.

In Yunnan schools this year, teachers are being trained with a sex education curriculum created by the conservative Christian group Focus on the Family. The agreement with the Yunnan ministry of education is a milestone for Focus on the Family, which has struggled for four years to make inroads on abstinence in China.

It is also the result of a narrow confluence of interests: Evangelical Christian groups want an entree into China. And Chinese authorities, despite the country's official atheism, want help with controlling population growth and managing the society's rapidly shifting values.

Chinese society has undergone major changes in recent decades, with divorce rates climbing steadily and migration and modernization putting increasing pressure on families, sociologists say. Wading into those waters, Focus on the Family has tried to market its marriage- and family-oriented programs as solutions. But Communist Party officials have been suspicious, at times, of the group's motivations.

At an early demonstration of the abstinence curriculum two years ago - given to the Communist Youth League of China in Hangzhou - teens were supposed to end the seminar by making a virginity pledge, the hallmark of the Christian group's abstinence program. But government officials quickly stepped in, insisting that the kids pledge to no one but the Communist Party.

"It hasn't been easy," said Deanna Go, China outreach director for the Colorado-based organization. "Everything takes longer here."

Officials in Yunnan, however, said Focus on the Family's message of abstinence resonated with the province's conservative leadership.

"Nowadays, teenagers have too many different channels for learning about sex," said Ma Lianhong, Yunnan's former secretary general of media, who introduced the Christian group to provincial leaders. "Even if you don't talk about it, they will just learn about it quietly by themselves, which is even more dangerous. . . . Abstinence is good for keeping the families steady and bringing down the divorce rate. And it complies with China's traditional morals."

Abstinence programs have generated considerable controversy in the United States and beyond. Critics point to research they say demonstrates that the approach is ineffective and argue that efforts should be geared instead toward safe-sex education. But proponents say the strategy has the potential to reduce the rates of out-of-wedlock births and sexually transmitted diseases.

In the past decade, Focus on the Family has found relative success with its abstinence program in other countries - notably majority Muslim nations such as Egypt and Malaysia, where its Christian brand of abstinence coincides with the teachings of Islam. Worldwide, the group says it has reached nearly 3 million teens.

China, however, has proved a tough market to crack. Premarital sex has become common in its developed cities. Even in the more rural areas, experts say, sexual mores are changing at a rapid pace. Condom companies are vying to capture a lucrative share of China's population of 1.3 billion. The United Nations, HIV-prevention groups and others are pouring millions into safe-sex programs. And abstinence, some say, is the last thing on Chinese teenagers' minds.

"It's hard convincing them to come to our training," said Qian Honglin, founder of a nonprofit group that is working with Focus on the Family in Beijing. "Their parents want them to come, but young adults don't listen to their mothers. . . . Once we get them in, however, it's easy for them to see the benefit."