California Governor Gavin Newsom is calling for a November 4 special election on new US House maps designed to win more Democratic seats.

His move is in response to Republican efforts to pick up five seats in Texas. Newsom released a campaign ad on social media on Thursday as Democrats kicked off a press conference.

State lawmakers technically need to declare the special election, and they plan to do so next week.

Democrats have not yet released their draft maps, but they aim to pick up five more seats.

The maps need voter approval. That's because voters previously granted the power to draw maps to an independent commission instead of lawmakers.

'Liberation Day for California'

Newsom said he would ask voters to approve new maps that would effectively neutralise changes Texas is planning that are expected to give Republicans more seats in the House of Representatives.

"Today is Liberation Day in the State of California," Newsom told supporters at the Democracy Centre in Los Angeles.

"Donald Trump, you have poked the bear, and we will punch back," he said, a reference to the animal that symbolises the 39-million-strong state.

Newsom, who is believed to harbour Oval Office ambitions, has emerged as a leading anti-Trump voice from a Democratic Party still floundering after last year's ballot box drubbing.

The two men have frequently locked horns, including over aggressive immigration enforcement raids the administration ordered in Los Angeles.