PHOENIX -- Phoenix Mayor Phil Gordon and Maricopa County Sheriff Joe Arpaio are trading barbs again about the enforcement of immigration laws.

The latest exchange was triggered by Arpaio's announcement earlier this week that he plans another crime suppression sweep. Critics contend four previous sweeps -- in Phoenix, Guadalupe and Mesa -- were aimed at illegal immigrants and amounted to racial profiling.

Arpaio said this week he would not inform local officials about future crime sweeps, and that prompted a message from Gordon, who said the sheriff should "work with local police officers and departments, not just calling ahead, but coordinating and letting them know where he's going to conduct all his different operations so as not to risk the lives of undercover officers, his deputies and the public."

Gordon said the sheriff has wasted too much time and money on operations like his recent crackdown on food vendors, and violent crime in the county is nearing "crisis levels." He said deputies' time would better be used "tracking down those criminals who are terrorizing our city."

Arpaio responded that Gordon's claims are "patently untrue" and said the mayor owes an apology to his deputies. He said violent crimes -- including murder and rape -- have declined by 10 percent over the past year in unincorporated areas of Maricopa County, about 8,000 square miles with a population of about 300,000. The number of priority 911 calls to the Sheriff's Office are down by 27 percent, Arpaio said.