By David Shepardson and Nandita Bose

WASHINGTON (Reuters) - California asked to join the U.S. Department of Justice's antitrust lawsuit against Google on Friday, making the state's attorney general the first Democrat to openly support the litigation.

The department in October accused the $1 trillion California-based company of illegally using its market muscle to hobble rivals, and was joined by 11 other states when it was filed.

"California is not making substantive changes to the complaint. In particular, California is not seeking to add any new facts or claims," Attorney General Xavier Becerra said in the filing, adding that it would not delay the case.

Google has denied wrongdoing, and the company has said that its search engine and other products are dominant because consumers prefer them.

"People use Google because they choose to, not because they're forced to, or because they can't find alternatives," a Google spokeswoman said. "We’ll continue to make our case in court."

The company must respond to California's request to join the lawsuit by Dec. 18, said the judge in the case, U.S. District Judge Amit Mehta.

The Justice Department welcomed California's entry to the case, which says Google broke antitrust law to build and maintain dominance in search and search advertising.

"This landmark antitrust case reflects broad and bipartisan concerns that Google ... has maintained its monopoly power by cutting off its competition," said spokesperson Brianna Herlihy.

In November, Reuters reported a separate bipartisan group https://reut.rs/34lxt03 of states plan to file a related lawsuit. The group, made up of Colorado, Iowa, Nebraska, New York, North Carolina, Tennessee, and Utah, plans to combine its case with the federal government's case.

California's Becerra has been picked by President-elect Joe Biden as his nominee for secretary of health and human services - a prominent member of the health team to lead the response to the coronavirus pandemic.

(Reporting by David Shepardson and Nandita Bose; additional reporting by Diane Bartz, Editing by Leslie Adler and Grant McCool)