US ATTORNEY General Jeff Sessions was expected to talk to police officials in Sacramento, California, today as the federal government sues the state for enacting laws that protect people living in the country illegally.

It is the most severe act yet in the Trump administration’s bid to force so-called sanctuary cities and states to co-operate with immigration authorities.

The US Justice Department is challenging three California laws that, among other things, bar police from asking people about their citizenship status or participating in federal immigration enforcement activities.

The lawsuit filed in federal court in Sacramento says the laws are unconstitutional and have kept federal agents from doing their jobs.

“The Department of Justice and the Trump administration are going to fight these unjust, unfair and unconstitutional policies that have been imposed on you,” Mr Sessions is due to tell police chiefs. “I believe that we are going to win.”

California officials remained defiant, with Democratic Governor Jerry Brown mimicking President Donald Trump on Twitter as he criticised Mr Sessions for coming to Sacramento “to further divide and polarise America. Jeff, these political stunts may be the norm in Washington, but they don’t work here. SAD!!!”

State attorney general Xavier Becerra, an elected official, said the state is on firm legal footing. “Our track record so far when it comes to any dispute with the federal government has been pretty good,” he said.

US Immigration and Customs Enforcement has said it will increase its presence in California and Mr Sessions wants to cut off funding to jurisdictions that won’t co-operate.