Arizona appeals against blocks on immigration law
Arizona's governor has appealed against a federal court's decision to block parts of an anti-immigration law hours before it came into effect.
The court issued a temporary injunction against a requirement that police check the immigration status of suspects they stop while enforcing other laws.
A section making it a crime not to hold immigration papers was also blocked.
The ruling is seen as a warning to other states considering Arizona-style immigration strictures, analysts say.
Lawyers for Republican governor Jan Brewer and the Arizona government filed their appeal at the 9th Circuit Court of Appeals in San Francisco on Thursday.
"I have also asked the 9th Court to expedite the briefing schedule and its ruling, since Congress and the president have once again failed to act," Ms Brewer said in a statement.
On Wednesday, she described the court's decision to block part of the law as a "bump in the road", saying the fight was "far from over".
Commentators are already predicting the legal battle could eventually go all the way to the Supreme Court.
Hundreds of protesters gathered in Arizona's state capital, Phoenix, on Thursday to demonstrate against the law. Police made dozens of arrests.
Hispanic groups have called Arizona's immigration law racist, but its supporters say it is a legitimate attempt to deal with the problem of illegal immigration.
Among the provisions kept was one making it illegal to transport and harbour illegal immigrants.
Also allowed to stand was a section of the law making it illegal for drivers to pick up day labourers from the street.
These parts of the law came into effect on Thursday.
The Republican-controlled Arizona legislature passed the law in April, amid fears of rising crime caused by illegal aliens and complaints the federal government had failed to act on the matter.
The injunction is a temporary measure until the judge can decide on the law's constitutionality.
Polls suggest a majority of Americans favour such measures on immigration, and several other states have been considering following Arizona-style strictures.
In light of the Arizona decision, those states are likely to reconsider.
In her decision, US District Judge Susan Bolton said the blocked sections of the law pre-empted the federal government's authority to set immigration law.
Among the controversial sections blocked was one making it a crime for undocumented workers to seek or apply for a job and another allowing police to arrest without a warrant people whom they had probable cause to believe had committed a crime for which they could be deported.
The US was likely to "suffer irreparable harm" if she did not block enforcement of those sections, the judge wrote.
"Requiring Arizona law enforcement officials and agencies to determine the immigration status of every person who is arrested burdens lawfully present aliens because their liberty will be restricted while their status is checked," she added.
She also wrote that the surge in requests for immigration status checks would force the federal government to shift resources away from its own priorities.
The US justice department hailed the ruling, while acknowledging "the frustration of Arizonans with the broken immigration system".
The Mexican government, which has repeatedly expressed concerns about the Arizona law, called the ruling a "first step in the right direction".