California's governor said he will ask voters to approve a ballot measure in November redrawing the state's congressional map in a way likely to create five more Democratic seats, escalating a redistricting war with the Republican-led state of Texas and President Donald Trump.

Texas Republicans have drawn a new congressional map aimed at flipping five Democratic seats in the November 2026 midterm election, with the battle for control of the US House of Representatives expected to be closely fought.

Governor Gavin Newsom and other California Democrats on Friday characterised their latest effort as an "emergency", a temporary strategy to neutralise Republican moves they see aimed at gaming the system.

"We are trying to defend democracy, as opposed to seeing it destroyed district by district," Newsom said in Sacramento, flanked by Democratic leaders of the California legislature and members of the state's congressional district, including former US House Speaker Nancy Pelosi.

The Democrats said they expected to have a newly agreed-upon map, based on previous plans reviewed by the state's independent redistricting commission, ready for public scrutiny next week, three months before it would go to voters.

The Democratic-majority legislature would first have to vote in favour of a special election, to be set for the first week of November.

Newsom was joined by half a dozen of the more than 50 Democratic Texas lawmakers who collectively left their home state to prevent the legislative quorum required for Republicans there to win adoption of a Texas redistricting plan championed by Trump.

Newsom and California's Democrats insisted they remain committed to the independent redistricting process enacted by state voters more than 15 years ago.

Republican leaders sought on Friday to ramp up pressure seeking to force the wayward Texas Democrats, holed up in such Democratic-led states as California, Illinois and New York, to return to the legislature and punish those who refuse.

Texas attorney-general Ken Paxton filed a lawsuit with the Texas Supreme Court seeking a declaration that the seats of 13 absent Democratic lawmakers are vacant.

Texas House of Representatives Speaker Dustin Burrows put the absent Democratic lawmakers on notice that they can only collect their pay cheques by appearing in person at the capitol in Austin.

Republicans now hold a narrow 219-212 majority US House of Representatives.

Texas Republicans' new redistricting map was the first salvo in trying to secure their party's majority on Capitol Hill. Trump hopes that with the redrawing of congressional district lines Republicans can expect to pick up as many as five additional US House seats.

Friday's response by Newsom and his fellow California Democrats may not be the last move in the redistricting game.

Other Democratic governors have threatened to follow suit, while Republican leaders in other states have said they may do likewise. (Reuters)