WASHINGTON/SAN FRANCISCO (REUTERS) - The US Justice Department will file a lawsuit against the state of California alleging it is interfering with the enforcement of federal immigration laws, escalating a long-simmering battle over "sanctuary" policies that try to protect illegal immigrants against deportation, senior department officials said on Tuesday (March 6).

The lawsuit, to be filed sometime late Tuesday in federal court in Sacramento, the California state capital, will take aim at three state laws passed last year that the Justice Department contends violate a clause in the US Constitution.

The issue of illegal immigrants has become increasingly heated since Donald Trump became president last year and signaled that he planned to target a wider swath of people for deportation.

Trump's attorney general, Jeff Sessions, has made combating illegal immigration one of his top priorities since taking over the helm of the Justice Department in February 2017. A key part of that effort involves a crackdown on primarily Democrat-governed cities and states that Sessions claims are"sanctuaries" that protect illegal immigrants from deportation.

Sessions is expected to formally announce the lawsuit, which will name as defendants the state of California, Governor Jerry Brown and the state's attorney general, Xavier Becerra, during a speech on Wednesday morning in Sacramento.

Brown in October signed into law a bill that prevents police from inquiring about immigration status and curtails law enforcement cooperation with immigration officers.

The Justice Department lawsuit will cite a provision of the US Constitution known as the "Supremacy Clause," under which federal laws trump state laws.

"The Department of Justice and the Trump administration are going to fight these unjust, unfair and unconstitutional policies that have been imposed on you," Sessions plans to tell a group of law enforcement officers, according to prepared remarks seen by Reuters.

Early into his tenure, Trump signed an executive order that sought to block municipalities that failed to cooperate with US immigration authorities from receiving federal grant funding.

However, the Justice Department's attempts to carry out the order to date have been stymied by lawsuits in the federal courts in Chicago, San Francisco and Philadelphia.

At issue is whether sanctuary cities are violating a federal law that requires them to share information about people they arrest with the U.S. Immigration and Customs Enforcement agency.

The Justice Department is already embroiled in several pending legal battles with the Trump administration related to sanctuary policies.

One case is now on appeal, after a federal judge in San Francisco blocked Trump's executive order to block funding to sanctuary cities.

Another case in San Francisco argues that the Justice Department's efforts to cut off funding rests on a flawed interpretation of federal immigration law and tramples California's right to enforce its own laws as it sees fit.

Similar kinds of cases are under way in other parts of the country, including a case on appeal in Chicago after a federal judge issued a nationwide injunction barring the government from blocking grant money typically used to help local police combat violent crime and help victims.

The Justice Department's planned lawsuit against California will target three state laws, senior Justice Department officials said on Tuesday in a press briefing.

One law, known as Assembly Bill 450, prohibits private employers in California from voluntarily cooperating with federal immigration officials and imposes fines of up to US$10,000 if a business owner fails to comply.

A second law, Senate Bill 54, prevents state and local law enforcement from giving federal immigration officials information about when they intend to release an illegal immigrant from their custody.

The third law, meanwhile, empowers the state to inspect federal immigration detention centers.

Collectively, the Justice Department officials said, these three laws improperly attempt to regulate federal immigration at the state level.

The department also plans to seek a court order from a judge to temporarily block the state from enforcing the laws.