Phoenix ? Civil rights activists Wednesday warned that Arizona is inviting rampant racial profiling and police-state tactics if it enacts what would be the toughest law in the nation against illegal immigrants.

The measure — on the verge of approval in the Legislature — would make it a crime under state law to be in the country illegally. It would also require local police officers to question people about their immigration status if there is reason to suspect they are illegal.

Immigrants unable to produce documents showing they are allowed to be in the U.S. could be arrested, jailed for up to six months and fined $2,500.

“That is an unprecedented expansion of police power,” said Alessandra Soler Meetze, executive director of the American Civil Liberties Union of Arizona. “It’s giving police officers a green light to harass anyone who looks or sounds foreign.”

The ACLU and immigrant rights groups are demanding Republican Gov. Jan Brewer veto the measure if it reaches her. The Republican has not announced whether she will sign it, but said she is a strong supporter of pragmatic immigration laws.

Her predecessor, Janet Napolitano, a Democrat who is now President Barack Obama’s Homeland Security secretary, vetoed similar proposals.

Current law in Arizona and most states doesn’t require police to ask about the immigration status of those they encounter, and many police departments prohibit officers from inquiring out of fear immigrants won’t cooperate in other investigations.

The new measure would be just the latest crackdown of its kind in Arizona, which has an estimated 460,000 illegal immigrants.

State Sen. Russell Pearce, the bill’s sponsor, has been the driving force behind Arizona’s tough new measures, including a law copied in other states that punishes companies caught knowingly hiring illegal immigrants.

“I believe handcuffs are a great tool, but you have to put them on the right people,” said Pearce, a former cop who can list the local officers killed or wounded by illegal immigrants. “Get them off the police officers and put them on the bad guys.”

Anger over the porous Mexican border mounted last month when an Arizona cattle rancher was shot to death. Investigators said he may have been killed by drug runners working for cartels based in Mexico.

The new measure is supported by police unions representing rank-and-file officers, who deny they would engage in profiling.

It is opposed by police chiefs, who worry that the law would be too costly, that it would distract them from dealing with more serious problems, and that it would sow such distrust among immigrants that they would not cooperate with officers investigating other crimes.

Legal immigrants fear that the law would give officers easy excuses to stop them, and that even U.S. citizens could find themselves detained if they can’t prove their legal status.

“When they come up with these things, it doesn’t matter if I’m here legally,” said Jose Melendez, a 55-year-old naturalized U.S. citizen from Guadalajara, Mexico. “If they see a Mexican face and a Mexican name, they’ll ask for papers.”

Anti-immigration activists say the larger goal is to discourage illegal immigration by making the U.S. inhospitable.

“Most illegals would leave on their own if they felt the U.S. was serious about our laws,” said William Gheen, president of Americans for Legal Immigration Political Action Committee.

House Republicans passed the bill on a party-line vote Tuesday. The Senate approved it in February but must vote on changes made in the House before sending it to the governor.

The law also would crack down on employment for illegal immigrants by prohibiting people from blocking traffic when they seek or offer day labor on street corners.

Also, a judge could fine a city for not enforcing the immigration law vigorously enough.