China is tightening rules on foreign adoptions, barring parents who are unmarried, over 50 or obese, but says it will try to increase the number of children available to those who qualify, according to U.S. adoption agencies.

The move comes amid a surge in foreign applications to adopt Chinese children. The United States is the No. 1 destination for children adopted abroad, but the number going to Europe and elsewhere is rising.

The restrictions are meant to limit adoptions to "only the most qualified families," said the Web site of one agency, Harrah's Adoption International Mission in Spring, Texas.

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An employee of the government-run China Center of Adoption Affairs, the agency that oversees foreign adoptions, said it has issued new guidelines but refused to confirm the details released by the American agencies. He wouldn't give his name.

A U.S. Embassy spokesman in Beijing said it was looking into reports of the new regulations. He spoke on condition of anonymity in line with embassy rules.

The Chinese agency also is trying to increase the number of children available by creating a new charity to improve conditions in orphanages and "keep infants and young children alive and well enough to be adopted," Harrah's said.

Americans adopted 7,906 children from China in 2005, raising the total since 1989 to 48,504, according to the Joint Council on International Children's Services in Alexandria, Va., an association of adoption agencies and parents' groups. The group's Web site lists 110 U.S. groups that arrange adoptions from China.

Under the new rules, only people who have been married for at least two years will be eligible to adopt, according to Harrah's, the New Beginnings Family and Children's Services Inc. of Mineola, N.Y., and Families Thru International Adoption Inc. of Evansville, Ind.

Beijing previously allowed adoptions by unmarried foreigners.

The agencies said Chinese officials disclosed the rules at a Dec. 8 meeting in Beijing. They take effect May 1.

Among other restrictions, couples must have a Body Mass Index — a measure of obesity — of no more than 40 and be aged 30-50, with people up to age 55 considered for children with special needs, according to the agencies.

The rules bar parents who take medication for psychiatric conditions including depression and anxiety or have "severe facial deformity."

Many Chinese children adopted abroad are girls who are given up by couples who, bound by rules that limit most urban families to one child, want to try for a son. Others are left at orphanages or by the roadside by unmarried mothers or poor families.

A sharp increase in foreign applications for adoption has led to a backlog in approvals, with waiting times rising from six months in early 2005 to as much as 15 months now, according to adoption agencies.