The Justice Dept. has filed a lawsuit seeking to bar Arizona's new immigration law from taking effect, contending that the state statute is unconstitutional and will "undermine" federal immigration enforcement.

At issue is Arizona Senate Bill 1070, which Gov. Jan Brewer (R) signed into law on April 23. The measure, which is to take effect on July 29, directs police, while stopping an individual, to try to determine that person's immigration status when there is "reasonable suspicion" that he or she is in the U.S. illegally.

The Arizona law could have a long-term effect on the state's construction industry, officials say.

In its complaint, filed July 6 in U.S. District Court in Arizona against the state and Brewer, the Justice Dept. says, "In our constitutional system, the federal government has preeminent authority to regulate immigration matters."

Attorney General Eric Holder said, "Arizonans are understandably frustrated with illegal immigration and the federal government has a responsibility to comprehensively address those concerns." But Holder added, "Setting immigration policy and enforcing immigration laws is a national responsibility."

Arizona's U.S. Senators, Jon Kyl and John McCain, both Republicans, issued a joint statement saying, "The Obama administration has not done everything it can do to protect the people of Arizona from the violence and crime illegal immigration brings to our state. Until it does, the federal government should not be suing Arizona on the grounds that immigration enforcement is solely a federal responsibility."

The government is seeking a temporary and permanent injunction against the Arizona law.

The federal brief adds, "Although states may exercise their police power in a manner that has an incidental or indirect effect on aliens, a state may not establish its own immigration policy or enforce state laws in a manner that interferes with the federal immigration laws."

It says, "The Constitution and federal immigration laws do not permit the development of a patchwork of state and local immigration policies throughout the country."

The state law, the complaint says, will put "significant and counterproductive burdens" on federal immigration agencies and divert resources from "dangerous aliens" who are the top federal immigration enforcement priorities.