Arizona migrant law may waste resources: Napolitano

People stage a protest against Maricopa County Sheriff Joe Arpaio during a news conference about Arpaio's 12th crime-suppression operation in Surprise, Arizona October 16, 2009.

WASHINGTON (Reuters) - A new Arizona law aimed at cracking down on illegal immigrants could divert resources from pursuing those in the country illegally who have committed more serious crimes, U.S. Homeland Security Secretary Janet Napolitano said on Tuesday.

The new law, set to take effect later this year in the state bordering Mexico, requires police there to determine if people are in the country illegally, but critics have said it enables racial profiling and may be unconstitutional.

The Obama administration is reviewing its options for possible challenges to the new state law and Napolitano told U.S. senators that its resources for pursuing more dangerous criminals committing felonies could be sapped.

"We have some deep concerns with the law from the law enforcement perspective because we believe it will detract from and siphon resources that we need to focus on those in the country illegally who are those committing the most serious crimes," she told the Senate Judiciary Committee.

The Arizona law requires police officers to arrest those unable to provide documentation proving they are in the country legally. It also makes it a crime to transport someone who is an illegal immigrant, and to hire day laborers off the street.

"We have concerns that at some point we'll be responsible to enforce or use our immigration resources against anyone that would get picked up in Arizona," Napolitano said.

Furor over the law has jump-started new efforts in Washington to pass comprehensive immigration reform. While this has been a priority for President Barack Obama, he has faced opposition from conservative Republicans over the details.

Republican Senator Lindsey Graham, who had been working with Democrats on crafting a compromise measure, warned Napolitano that more reassurances are needed about stemming the tide of illegal immigrants entering the country.

"I bet you everything I own if you bring it up in this environment, not having done anything that is going to reassure the American public that we won't have 20 million more (illegal immigrants), you're going to crash and burn," he told her.

The battle for reform has also been complicated by Mexican drug cartel violence spilling over the border into the United States. There were an estimated 10.8 million illegal immigrants living in the United States on January 1, 2009, with some 460,000 undocumented immigrants in Arizona.

Napolitano, once the Democratic governor of Arizona, said she supported reform that allowed illegal immigrants already in the United States to seek citizenship on condition that they pay a fine and relevant taxes and penalties, learn to speak English, and are barred from jumping ahead of others who have used legal routes to apply.

(Editing by Eric Walsh)