The Virginia State Police have backed off a plan that would have allowed some officers to make immigration arrests, a prospect that had been fiercely opposed by immigrant rights advocates.

The state police chief, Col. Steve Flaherty, said last week that his department has decided against proceeding with an agreement with federal authorities that would have made Virginia the third state in the nation to adopt such a practice.

"We're not moving forward with it at this particular point in time," he said in an interview.

The idea of involving police in immigration enforcement has attracted growing interest since the Sept. 11, 2001, terrorist attacks, which were carried out by 19 foreigners, three of them in the country illegally. Florida and Alabama have signed agreements with the Department of Homeland Security under which dozens of their police officers have been authorized to make immigration arrests, typically a federal responsibility.

"We have municipalities and states approach us all the time and inquire about it," said Manny Van Pelt, a spokesman for Immigration and Customs Enforcement, which is part of Homeland Security.

But several localities that expressed interest in the idea have ultimately abandoned it because of a lack of resources or opposition from immigrant groups worried about ethnic profiling. Even police have been split over whether it makes sense.

Virginia offers an example of the sensitivity surrounding the issue: While state police were negotiating their agreement last year with Homeland Security officials, the Virginia legislature passed a bill giving local and state police slightly more power to enforce immigration law.

Immigrants panicked, despite the fact that the Virginia law was very narrowly drawn. It allowed police to arrest only convicted felons who had re-entered the country illegally after being deported.

"It created a huge problem for us when the law was first passed," said Col. Rick Rappoport, police chief in the city of Fairfax. Rumors swept through ethnic communities that anyone lacking proper documents could be picked up, prompting some immigrants to stop dealing with law enforcement authorities. A few even hid at home and hoarded food, police said.

Immigrant advocacy groups in Virginia expressed alarm about the potential for misuse of the new law and pressed state police not to seek further immigration authority.

"A number of the police we met with realized if they want immigrants to report crimes and be witnesses, they can't be in fear of being arrested," said Deborah Sanders, executive director of the Capital Area Immigrants' Rights Coalition.

Flaherty, the state police chief, said he was sensitive to the immigrant groups' concerns. But putting on hold the federal agreement, which would have given the extra authority to at least two dozen of his officers, was "more of a practical decision," he said. He said authorities determined that the new Virginia law covered the kinds of immigrants that state police were worried about -- such as drug traffickers or gang members.

"We were really talking about being able to deal with the worst of the worst. That's the way HB 570 was framed," Flaherty said, referring to the state law by its legislative number.

However, nearly a year after it took effect, the state law appears to have been used rarely, if at all. Officials with nine police and sheriff's departments in Northern Virginia, home to the majority of the state's immigrants, said in interviews that they were not aware of a single arrest made using the additional authority.

"I think it's a useful tool, but the circumstances in which it can be used are so narrow that I think it's very unlikely the average patrol officer is going to encounter a situation that meets the criteria," Rappoport said.

Traditionally, local and state police could arrest immigrants for criminal offenses but not for civil immigration violations. Under a 1996 law, however, federal authorities can train police from state or local jurisdictions to enforce immigration law while carrying out other duties.

With the number of illegal immigrants soaring to an estimated 10 million, some officials think that local or state police should be enlisted to help the several thousand overwhelmed ICE agents who enforce immigration law.

"The federal government has completely dropped the ball," said Del. David B. Albo (R-Fairfax), who complained that illegal immigrants are a financial drain on such areas as Northern Virginia because they use taxpayer-funded schools and hospitals. "What we need to do is take control of this."

Albo sponsored last year's House measure to grant slightly more immigration authority to local and state police. He is currently drawing up more ambitious legislation that would make it a violation of Virginia law for illegal immigrants to even be in the state. Under his proposal, he said, police could file this charge only against immigrants already accused of other crimes.

Federal legislators are also moving to enlist more local police in the detention of illegal immigrants. Last month, the House passed an amendment stating that local and state police have "inherent authority" to enforce immigration laws, even without an agreement with Homeland Security. The Senate has not acted on the measure.

"Our ICE agents are wonderful but simply do not have the physical ability to be in every place to work on enforcement," said Rep. Lynn A. Westmoreland (R-Ga.) during the debate on the amendment.

But several localities across the country have run into difficulties when they tried to gain an expanded immigration role for police.

Last November, for example, Steve Levy, executive of Suffolk County on New York's Long Island, withdrew a proposal to get police certified to enforce immigration law after the idea was attacked by legislators, Latino groups and even the local Police Benevolent Association.

The mayor of Danbury, Conn., also recently proposed setting up such a program for state police. But Richard Blumenthal, state attorney general, opposes the idea, which would need approval from the Connecticut legislature.

Some police say they simply don't have the resources to be part of the federal program, which typically requires officers to undergo five weeks of ICE training in immigration and civil rights law -- and with the police picking up some of the tab.

"I don't know many state police or highway patrols who can give up people for five weeks," said Gary Adams, chief of the Oklahoma Highway Patrol, who said he had been briefed on the program but decided against pursuing it.

Even those states and counties considering joining the federal program said they envision using the added authority in limited cases.

"We don't want to become federal immigration officers," said Jon Fleischman, a spokesman for the Orange County, Calif., sheriff's department, which is considering training some officers in immigration law.

Several of the police and sheriff's departments in Northern Virginia said they were not interested in gaining the additional authority.

"We're not advocating, supporting or facilitating illegal immigration," said Dave Rohrer, chief of the Fairfax County police.

But, he added: "Our job is to protect people. And I'm concerned that people who are victims of a crime, whether citizens or not, are not calling us because they're afraid we're going to check [legal] status only."

"The federal government has completely dropped the ball," said Del. David B. Albo (R-Fairfax). He said illegal immigrants are a financial drain on taxpayers.