US President Donald Trump said on Wednesday he has ordered a halt to federal disaster relief for California's wildfires unless state officials involved in forest management "get their act together".

"Billions of dollars are sent to the State of California for Forest fires that, with proper Forest Management, would never happen," Trump wrote on Twitter, a day after western governors asked for greater federal investment in fire prevention.

"Unless they get their act together, which is unlikely, I have ordered FEMA to send no more money. It is a disgraceful situation in lives & money!" the president said, referring to the Federal Emergency Management Agency.

California has suffered a series of increasingly massive, deadly blazes in the past two years that have destroyed homes and businesses and put burned areas at a greater risk of mudslides.

Governor Gavin Newsom said 167 people have been killed by fires and floods over that time.

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Trump's move targets a state that is home to some of his biggest political rivals, including Democratic US House of Representatives Speaker Nancy Pelosi, who is leading the fight in Congress against Trump's demands for $5.7bn in funding for a border wall on the Mexican border.

Writing on Twitter, Pelosi blasted Trump, saying his "threat insults the memory of scores of Americans who perished in wildfires last year & thousands more who lost their homes".

.@realDonaldTrump’s threat insults the memory of scores of Americans who perished in wildfires last year & thousands more who lost their homes. @GOPLeader must join me to condemn & call on POTUS to reassure millions in CA that our govt will be there for them in their time of need https://t.co/YZJQug9zh0 — Nancy Pelosi (@SpeakerPelosi) January 9, 2019

Newsom, also a Democrat, said at his swearing-in ceremony this week that the Trump administration is "hostile to California's values".

'Dangerously wrong'

FEMA, which provides grants for home repairs or rental assistance after disasters, said it could not respond to queries about Trump's order due to the partial government shutdown, and it was unclear whether there would be any immediate effect.

More than half of the 13.4 million hectares (33 million acres) of forest in California are managed by federal government agencies, according to the University of California's Division of Agriculture and Natural Resources.

State and local agencies control only three percent, and the rest is privately controlled.

On Tuesday, the governors of California, Oregon and Washington asked federal agencies to "double" their investment in forest management in a letter to the White House.

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California plans to spend $1bn on forest management over the next five years, the letter said, and has spent $111.3m since 2017, just under half on federal lands.

During a November tour of the wreckage of the Camp Fire, the deadliest in California history, Trump blamed what he called poor forest management for the fire, and threatened to end FEMA funding.

The California Professional Firefighters organisation, with more than 30,000 members, said at the time Trump's assertion was "dangerously wrong".