The U.S. Justice Department has decided to file a lawsuit challenging the southwestern U.S. state of Arizona's controversial new immigration law.
Sources with the justice department have told reporters the suit will argue that enforcing immigration is a federal responsibility and the Arizona law intrudes on that authority.
The Arizona law, due to take effect later this month, requires police to examine a person's immigration status if there is reasonable suspicion the person is in the country illegally. It will also make illegal immigration a state crime.
The lawsuit has been expected for weeks.
U.S. President Barack Obama has called the Arizona measure "misguided," and civil rights groups say the law would lead to race-based discrimination.
Supporters say the Arizona measure is a valid response to the issue of illegal immigration.
The supporters say the federal government has not done enough to combat the problem and that the law will help fight crime blamed on illegal immigrants.
The lawsuit could be filed as early as Tuesday.
Some information for this report was provided by AP.