(AP) Gov. Janet Napolitano vetoed a bill that would have criminalized the presence of illegal immigrants in Arizona, citing opposition from police agencies that want immigration arrests to remain the responsibility of the federal government.

The proposal would have expanded the state's trespassing law to let local authorities arrest illegal immigrants anywhere in Arizona, the nation's busiest illegal entry point. Congress also had considered criminalizing the presence of illegal immigrants in the country.

In a letter to lawmakers, Napolitano said she opposes automatically turning all immigrants who sneaked into the state into criminals and that the bill provided no funding for the new duties.

"It is unfortunate that the Legislature has once again ignored the officials who are most directly affected by illegal immigration and instead has passed yet another bill that will have no effect on the problem but that will impose an unfunded burden on law enforcement," Napolitano wrote Monday.

Supporters said the bill would have given Arizona a chance to get a handle on its vast border problems by providing a second layer of enforcement to catch the tens of thousands of immigrants who slip past federal agents each year.

Republican Sen. Barbara Leff of Paradise Valley, who proposed the bill, said the governor has painted herself as tough on illegal immigration by declaring a state of emergency at Arizona's border, but has taken little action to back up her rhetoric.

"I don't think the governor wants to do anything about this problem," Leff said. She said the bill would have been a means to detain illegal immigrants until federal agents can pick them up.

The Democratic governor, accused by her Republican critics of being soft on immigration, has vetoed other immigration bills from the GOP-majority Legislature within the past year, including a proposal to give police the power to enforce federal immigration laws.

While immigrants provide the economy with cheap labor, Arizona spends tens of millions of dollars each year in health care and education costs for illegal workers and their families. An estimated 500,000 of the state's population of about 6 million are illegal immigrants.