California State Attorney General Xavier Becerra. Jason Doiy / The Recorder

California Attorney General Xavier Becerra is preparing to sue to block the first phase of President Donald Trump’s planned wall along the Mexican border, state officials said Wednesday morning.

Becerra is scheduled to appear Wednesday morning at Border Field State Park in San Diego County, a coastal destination where visitors can see the fenced line separating Mexico and the United States.

Becerra’s office did not immediately disclose the substance of the suit or name the court where it will be filed. A brief statement said the complaint will challenge the Trump administration’s plans “to begin construction of border wall projects” in San Diego and Imperial counties.

Over the last two weeks, U.S. Customs and Border Protection awarded contracts with six companies to build 30-foot sections of “model” walls along California’s southern border, according to The San Diego Union-Tribune. The agency has not announced when construction will be begin, although the Wall Street Journal obtained a memo indicating work would start on Sept. 26.

Becerra, like most Democratic politicians in California, has made no secret of his contempt for Trump’s border wall plans. Shortly after he was appointed attorney general in January, Becerra said on the NBC News program Meet the Press that any wall would have to comply with California’s environmental and public safety laws.

“There are any number of hurdles that a federal administration would have to jump before they can build a medieval wall that will probably never work,” he said.

Environmental groups last week sued the federal government after the Trump administration waived environmental rules to speed up construction of the model walls.

Becerra’s office has filed or is participating in a number of suits around the country that challenge Trump administration immigration policies.

Last week, Becerra filed a suit in San Francisco federal court challenging the White House decision to rescind the Deferred Action for Childhood Arrivals program, which let hundreds of thousands of children of undocumented immigrants apply for temporary reprieval from deportation.

“When the Trump administration rescinded DACA, they didn’t just threaten the futures of hundreds of thousands of young Americans,” Becerra told reporters at a news conference. “The Trump administration also broke the law.”

State lawmakers last week voted to declare California a “sanctuary state”—a move that would limit local law enforcement agencies’ cooperation with federal immigration officials. The California Values Act passed the Senate 27-11 early Saturday on a partisan vote..

U.S. Attorney General Jeff Sessions, addressing federal law enforcement in Portland, Oregon, on Tuesday, inveighed against sanctuary cities. He pointed to a recent San Francisco shooting death—allegedly by a man facing deportation—of a community volunteer named Abel Esquivel.

“Sadly, after these tragic cases, the legislature in California—where these tragedies occurred—has now passed legislation to further limit law enforcement cooperation with immigration enforcement,” Sessions said in prepared remarks. He called the legislation an “unconscionable reaction,” after the shooting, “to put into law the very policies that got him killed.”