SAN FRANCISCO, Jan. 17 (Xinhua) -- London Breed, the acting mayor of U.S. western coastal city of San Francisco on Wednesday urged U.S. Congress to pass a "clean Dream Act" to protect undocumented immigrants amid reports that immigration authorities are planning a massive sweep on illegal immigrants in the state of California.

"Dreamers are our friends, neighbors and members of our communities. We are urging Congress to pass a clean #DreamActNow," Breed tweeted.

Dreamers refer to a group of undocumented immigrants who were brought to the United States as children.

By October 2017, about 690,000 young adults were currently protected under the Deferred Action for Childhood Arrivals (DACA), an immigration program established by former U.S. President Barack Obama in 2012 but revoked by President Trump in September 2017.

"We need comprehensive immigration reform, not shortsighted and misguided policies," Breed said in her tweet Wednesday.

She also said on Tuesday that "San Francisco is and will always be a Sanctuary City" to the Dreamers.

"We will continue to fight for the hardworking immigrants that live in our City. We will continue to push policies that protect our immigrant communities," she noted.

Breed's statement came amid reports that U.S. federal immigration officials are reportedly preparing for a major sweep in northern California after Thomas Homan, director of the U.S. Immigration and Customs Enforcement (ICE), threatened to target California for becoming a sanctuary state.

The ICE plans to arrest more than 1,500 undocumented immigrants, mostly in the Bay Area in San Francisco, the local daily San Francisco Chronicle reported.

The sanctuary state law of California limits its cooperation with federal immigration authorities and forbids police from arresting people simply because of their undocumented status.