The Justice Department has decided to file suit against Arizona on grounds that the state's new immigration law illegally intrudes on federal prerogatives and will seek a preliminary injunction to stop the legislation from taking effect, law enforcement sources said Tuesday.

The lawsuit, which three sources said could be filed as early as Tuesday, will invoke for its main argument the legal doctrine of "preemption," which is based on the Constitution's supremacy clause and says that federal law trumps state statutes. Justice Department officials believe that enforcing immigration laws is a federal responsibility, the sources said.

But the filing is likely to have a civil rights component as well, arguing that the Arizona law would lead to police harassment of U.S. citizens and foreigners, said the sources, who spoke on condition of anonymity because the government has not announced its plans. President Obama has warned that the law could violate citizens' civil rights, and Attorney General Eric H. Holder Jr. has expressed concern that it could drive a wedge between police and immigrant communities.

A federal lawsuit will dramatically escalate the legal and political battle over the Arizona law, which gives police the power to question anyone if they have a "reasonable suspicion" that the person is an illegal immigrant. In addition to Obama and Holder, the measure has drawn words of condemnation from civil rights groups and has prompted at least five other lawsuits. Arizona officials have defended the law and urged the Obama administration not to sue.