Responding to public outcry about sexual abuse of foreign students in the United States, the Bush administration is today proposing new rules to screen host families and regulate agencies that sponsor some 28,000 high school exchange students, almost all minors, every year.

Although foreign students have been coming to the United States under formal exchange programs for more than a half-century, no sponsor has been required to keep figures on sexual abuse or report molestation cases to the federal government. Now they will.

Yet the rules could not have prevented three cases of abuse now in the courts.

Gaithersburg High School biology teacher Andrew Powers sneaked into the bedroom of the 17-year-old German girl living with his family in the middle of the night last December and tried to get her to perform oral sex, according to a police affidavit. When his wife wasn't home, Powers also "frequently" roamed the house naked in front of the student, the affidavit adds. Powers, who has resigned, is to be sentenced next week after pleading guilty to second-degree assault and fourth-degree sexual offenses. His attorney declined to comment.

The host father of a 16-year-old German girl in Plainwell, Mich., was charged in April with installing hidden cameras in her bedroom, first under her blankets, then in a dollhouse, to capture her naked. Dale Lacoss will be sentenced this month after pleading guilty to distributing the image of an unclothed person and possession of child sexually abusive material.

And this week, the coordinator for foreign exchange students in Sherwood, Ark., was charged with first-degree sexual assault for rape of three male European exchange students over the past year. In one case, during his wife's absence, Doyle Meyer Jr. held a slumber party for students, provided them with alcohol and then masturbated one of the minors against his will, according to the police affidavit. The student was reluctant to file charges until he heard about others Meyer allegedly molested.

Meyer could not be reached for comment.

Even under the new vetting procedures, the cases in Maryland, Michigan and Arkansas would not have been averted because the abusers had no criminal record and were not on the national offenders registry. And in the Gaithersburg case, Powers had passed a criminal background screening by the Montgomery County school system.

Foreign students are among the most vulnerable minors because they usually do not know U.S. laws, are unfamiliar with customs, are dependent on host families or sponsors, don't know what to do when abused or are afraid to act, according to Lt. Frank Baker of the Allegan County Sheriff's Office, who has been involved in the Michigan case.

"For a predator, this is the ideal situation," Baker said.

The proposed rules published today in the Federal Register, which are likely to go into effect after 30 days of public comment, come as the Bush administration pushes student exchanges as a centerpiece of its diplomatic outreach to improve the U.S. image abroad.

"I'm a huge proponent of exchanges, student exchanges, cultural exchanges, university exchanges. We talk a lot about public diplomacy," said Secretary of State Condoleezza Rice at a meeting with her staff days after taking over in January. "It's extremely important that we get our message out, but it's also the case that we should not have a monologue with other people. It has to be a conversation, and you can't do that without exchanges and openness."

A State Department spokesman described incidents of assault as "very rare." But groups advocating tougher rules to protect foreign students -- who can pay $6,000 or more to sponsoring agencies -- said most cases go unreported.

Frank Swiderski's abuse of a 17-year-old Vietnamese exchange student was detected in 2003, when an Eastlake, Ohio, police officer lectured to the boy's health class about sexual assault. The student asked if the practices by his host father -- nude massages, fondling and forcing him to shave Swiderski's pubic hair -- were normal.

At Swiderski's home, police found photos of nude boys -- many of whom appeared to be exchange students and some pictured with the former high school teacher -- that dated to the 1970s, according to Karen Kowall of the Lake County prosecutor's office. Swiderski was convicted and sentenced to 21/2 years for gross sexual imposition and pandering obscenity involving a minor, but attempts to contact former exchange students and get them to come forward failed, Kowall said.

Most cases reported in recent years involve host parents or personnel with sponsoring agencies.

In March 2004, California social studies teacher Peter Ruzzo was sentenced to three years in prison for having sex with a 15-year-old German student living in his home. Ruzzo told the victim "when he saw her foreign-exchange photo that he considered it a challenge, even before she got here, to have sex with her," Kelly Hansen, deputy district attorney in the case, told the North County Times. Ruzzo pleaded guilty to six counts of lewd acts with a child and one count of penetration with a foreign object.

The State Department decided that publishing the regulations was worthwhile even if they do not eliminate the problem. "We have had a lot of interest in this from concerned citizens. We heard their concerns, examined the situation fully and decided that if we can build in one extra bit of protection, it would behoove us to do it," said Stanley Colvin, director of the State Department office of exchange coordination.

Under the proposed rules, all adult members of host families and personnel in sponsoring groups will have to be vetted through the sex offender registry and for criminal history. Sponsors will have to report any allegation of sexual misconduct to local authorities and the State Department. "If they don't report, we'll close their program," Colvin said.

In their orientation, all foreign students also will be advised on inappropriate sexual contact and what they can do if anyone makes an abusive overture. "We want to be able to resolve any suggestions that this has been underreported," Colvin added. Because there is no database, "we're going to make our best effort to find out one way or another," he said.

Some groups, such as Bethesda-based Youth for Understanding, have been doing background checks for years. YFU uses the Internet to do a name check of all host family members. But Reed Rago, YFU's director of development, conceded that the system is not foolproof.

Concerned parents and others last month formed the Committee for Safety of Foreign Exchange Students, based in Oceanside, Calif., to provide guidance and protection against "a pattern of abuse that is making headlines around the world," it said in a news release.

The issue is also on the agenda for the first time at the October annual conference of the Council on Standards for International Educational Travel, a trade group established in 1984 and based in Alexandria. The group offers voluntary accreditation for most of the 100-plus exchange programs in the United States.

States have done little to address the issue. Three times since 2001, Oregon state Sen. Floyd Prozanski has introduced legislation requiring criminal background checks on host families but has failed to get the bill out of committee.

"For a young person, there's been no check on who families are. It's very unfortunate that we have a lot of individuals who are looking for opportunities" to exploit youngsters, said Prozanski, whose wife was a foreign exchange student in Argentina in the 1970s. "Unfortunately, it happens more frequently than we want to admit."

Penalties for sexual assault vary but often are not steep.

In 2003, David Goodhead of Riverside, Calif., pleaded guilty to abusing a 16-year-old Danish student living with him during a trip to Yosemite National Park. Goodhead was sentenced to 36 months' probation and a $1,500 fine.

In July 2004, Rotary Club exchange student coordinator James Anthony Dillon was sentenced to 30 months' probation, with 18 months' home confinement with an electronic monitor and a $2,000 fine, for three acts of molestation of a 17-year-old European student. As in many cases eventually reported, an American third party went to authorities.

Staff writers Ylan Q. Mui and Susan Kinzie contributed to this report.

Andrew Powers of Germantown admitted to sex offenses.Doyle Meyer Jr. is charged with assaulting three students.