Arizona Gov Jan Brewer is heading to San Francisco to appeal against a court's rejection of the state's strict new immigration law.
A judge ruled in July the law improperly usurped Washington's authority on immigration policy.
Among other provisions, it required police to check the status of suspects thought to be in the country illegally.
Gov Brewer, a Republican, argues the law is needed because Washington has failed to act on the issue.
The Republican-controlled Arizona legislature passed the law, one of the nation's strictest, in April, rejecting protests it would lead to the racial profiling of Hispanics and force legal immigrants to carry papers.
The Obama administration challenged the law in court, arguing immigration policy was the domain of the federal government.
In July a US district judge in Arizona threw out the most controversial parts of the law.
Judge Susan Bolton wrote the US was likely to "suffer irreparable harm" if she did not block enforcement of the law, and said the surge in requests requests for immigration status checks would force the federal government to shift resources away from its own priorities.
Among the controversial sections she 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.
A requirement that police check the immigration status of suspects they stop while enforcing other laws was also blocked.
Arizona appealed against Judge Bolton's ruling. The hearing in the 9th Circuit Court of Appeals is expected to begin on Monday morning in California. Gov Brewer's office announced last week she would attend the proceedings.
Gov Brewer, who is running for election to the post she assumed when her predecessor Janet Napolitano joined President Barack Obama's cabinet, declared the law had the "overwhelming support" of Arizona voters.
"America is not going to sit back and allow the ongoing federal failures to continue," she said in a statement. "If the federal government wants to be in charge of illegal immigration and they want no help from states, it then needs to do its job. Arizona would not be faced with this problem if the federal government honoured its responsibilities."
The border state is the biggest entry point into the US for illegal immigrants, and is home to an estimated 460,000 illegal immigrants.