HO CHI MINH CITY, Vietnam — Vietnam, where growing numbers of Americans have turned to adopt a baby, announced yesterday it is halting all U.S. adoptions following allegations of baby-selling, corruption, and fraud.

The abrupt cutoff cast a cloud of uncertainty over pending adoptions in the Southeast Asian country, which have surged in the face of tightened restrictions in China, Guatemala, and elsewhere.

The announcement came days after the Associated Press published details of an American Embassy report that outlined rampant abuses, including hospitals selling infants whose mothers could not pay their bills, brokers scouring villages for babies, and a grandmother who gave away her grandchild without telling the child’s mother.

“It is tragic for children that the U.S. government has not been able to find ways to work with the Vietnamese government to prevent adoption abuses while at the same time processing legitimate adoptions,” said Tom Atwood, president of the Washington-based National Council for Adoption, a research and advocacy organization.

“Many hundreds, perhaps thousands, of children will not have families as a result of this failure of leadership.”

American adoptions have boomed in Vietnam, with Americans — including actress Angelina Jolie — adopting more than 1,200 Vietnamese children over the 18 months ending in March. In 2007, adoptions quadrupled from a year earlier.

In its nine-page report, the American Embassy said some American adoption agencies paid orphanage officials as much as $10,000 a referral, while others took them on shopping sprees and junkets to America in return for a flow of babies.

It said questions arose after routine investigations turned up widespread inconsistencies in adoption paperwork. There was also a suspicious surge in the number of babies listed as abandoned, making it impossible to confirm the children were genuine orphans or that their parents had knowingly put them up for adoption, as required by America law.

The director of Vietnam’s International Adoption Agency, Vu Duc Long, called the American allegations “groundless.” Yesterday, he said Vietnam was scrapping a bilateral agreement with America that sought to regulate the adoption system.

The Americans “can say whatever they want, but we are not going to renew it,” Long said.

In a letter to the American Embassy in Hanoi, Vietnam said it would stop taking adoption applications from American families after July 1, but would continue to process applications of families matched with babies before that. Adoption arrangements with other countries were unaffected.

The American Embassy said it respected Hanoi’s decision, but was confident of the accuracy of the report.

“The government of Vietnam has made their own decision, but we believe that our report speaks for itself,” a spokeswoman, Angela Aggeler, said.

It was not immediately clear how many American couples were affected by the decision.

An executive director of a Washington-based international adoption agency, Linda Brownlee, said it was a bitter blow for 20 families on its waiting list who will not be able to be matched with children in time.