MEXICO CITY - Mexico joined a legal challenge to Arizona's controversial new immigration law on Tuesday, arguing that the measure is unconstitutional and would harm relations with the United States.

The Arizona law, which takes effect on July 29, makes it a crime to be in the state illegally. It requires state and local police, during lawful contact, to determine the immigration status of any person they suspect is in the country illegally.

It has been challenged in five separate lawsuits filed in federal courts in Arizona by civil rights and religious groups as well as two local police officers. Plaintiffs say the law is unconstitutional and a mandate for racial profiling.