Washington - Top Justice Department officials have drafted a legal challenge that could be filed in federal court in Arizona asserting that the state's new immigration law is unconstitutional because it impinges on the federal government's inherent authority to police the nation's Southwest border with Mexico, sources said Wednesday.

At the same time, the government officials said, the department's civil rights division is considering possible legal action against the law on the basis that it amounts to racial profiling of Latinos who are legally in Arizona but conceivably could be asked to provide documents proving their citizenship.

Attorney General Eric Holder on Wednesday met with 10 police chiefs who object to the law, and he promised them he would act on the recommendations "soon," a spokesman said. The police chiefs urged him and the Obama administration, which has reservations about the Arizona law, to stop it from going into effect because they said it would seriously hamper local police work if officers are asked to serve as border police.

"He did say that the Justice Department is seriously considering what they would do and that could come very soon," said Chuck Wexler, director of the Police Executive Research Forum, a think tank that helped coordinate the meeting between the police chiefs and Holder.

A dozen or more states are considering legislation mirroring the Arizona law, which goes into effect in July. That groundswell of support is part of what is pushing Holder and the White House to consider swift action against the Arizona law.

Matthew Miller, the Department of Justice's chief spokesman, acknowledged that Holder told the police chiefs that a decision on any federal action will come "soon."

But, Miller also cautioned that "the review is still on. There's really not been any decisions yet. We're still working on it, and it's still being discussed internally."

He declined to say whether a decision is imminent or discuss which proposals the department was leaning toward. Nevertheless, Miller said that the meeting with the police chiefs was very helpful. "The attorney general thought the police chiefs raised important concerns about the impact the Arizona law will have on the ability of law enforcement to keep communities safe," he said.

Echoing concerns from Obama and Holder, the chiefs told the attorney general during the closed-door meeting that the problem with the Arizona law is that it will break down trust between victims and witnesses of crimes and the police officers in their communities. Three of the chiefs meeting with Holder are from Arizona: Jack Harris of Phoenix, Roberto Villasenor of Tucson and John W. Harris of Sahuarita, who also serves as president of the Arizona Association of Chiefs of Police.

"The attorney general asked us very specific, good questions about our experiences, all the things we've heard, to get a good reading on the ground," Wexler said. "Beyond that he did not give us any indication of what the Justice Department is going to do.

"We were not trying to influence the attorney general as much as to have a conversation with him about our concerns and also get the (Obama administration) focused on the need for national legislation."

Beck said he too was unsure what Holder meant by "soon."

"The U.S. attorney general listened to us, we had a great conversation, but he was not committal," the Los Angeles chief said. "His task is to announce his plans to the American people, not necessarily to this group. I think that we influenced him, but we will see."

Under the Arizona law, police are required to ask people who are stopped because of a "reasonable suspicion" that they are in the country illegally for documents. The offense would be similar to criminal trespassing, and violators would then be turned over to federal authorities for deportation.

Despite the opposition to the law from the Obama administration, many Americans support it; some polls show that up to 70 percent are in favor of giving local police the authority to check on someone's legal status in the United States.

Likewise, not all top U.S. police officials are against the law. In Arizona, some wholeheartedly support it. They include Maricopa County Sheriff Joe Arpaio in the Phoenix area, who has long railed against the influx of undocumented immigrants there, and Pinal County Sheriff Paul Babeu, head of the Arizona Sheriff's Association.