SACRAMENTO/WASHINGTON (Reuters) - U.S. President Donald Trump lashed out once more at California on Wednesday for a series of devastating wildfires he blames on poor forest management, threatening to withhold federal disaster aid in a Twitter blast that drew rebukes from lawmakers in his own party.

But Trump’s tweet, the latest of several in recent months accusing California of bringing wildfires on itself, appeared to be a largely empty ultimatum, presuming presidential authority he lacks under federal statutes.

One such law expressly bars the president from acting to “delay or impede” disaster relief once a federal emergency or disaster declaration has been made.

Trump’s threat to withhold Federal Emergency Management Agency (FEMA) assistance to California came two days after newly elected Governor Gavin Newsom, a Democrat, used the occasion of his swearing-in to critique the “corruption and incompetence” of the Republican president.

Beyond Newsom, who has vowed to position California as a counterweight to Trump, the deeply blue state is home to some of the president’s most outspoken political foes, including U.S. House of Representatives Speaker Nancy Pelosi.

The San Francisco Democrat is leading the fight in the U.S. Congress against Trump’s demands for $5.7 billion in funding to build a wall along the U.S.-Mexico border, pitting congressional Democrats against Trump in a standoff leading to a prolonged partial closure of the federal government.

Pivoting from weeks of headlines dominated by the shutdown, Trump returned to his commentary that California’s supposed mishandling of its forests and water resources were chiefly to blame for a fire season that ranks as the most destructive on record.

“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 wildfire 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.

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Research shows the growing frequency and intensity of wildfires in California and other Western states are largely attributable to prolonged drought, symptomatic of climate change. The Trump administration has rejected or downplayed the role of climate change in the worsening wildfire picture.

Trump’s latest tweet drew a sharp reaction from the state Assembly’s top Republican and two Republican legislators representing the area around the northern California town of Paradise, which was mostly incinerated in a wildfire that killed 86 people and destroyed nearly 14,000 homes in November.

Trump toured the Camp Fire zone in November, promising “to take care of the people who have been so badly hurt.”

‘WHOLLY UNACCEPTABLE’

State Senator Jim Nielsen and Assemblyman James Gallagher said in a joint statement Trump’s threat to withhold FEMA funds from California “is wholly unacceptable.””He made a commitment to the people who have lost everything in these fires, and we expect the federal government to follow through with his promise.”

Fellow Republican Marie Waldron, the Assembly’s minority leader, said separately that anything less than total government support for the fire victims “is inappropriate and unhelpful.”

FEMA said it could not respond to queries about Trump’s order due to the partial government shutdown. Gallagher said FEMA centers around Paradise remained open on Wednesday.

U.S. Representative Doug LaMalfa, a Republican whose congressional district encompasses Paradise, also chided Trump, saying “threats to FEMA funding are not helpful and will not solve the longer-term forest management regulatory problems.”

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Experts agree much of California’s forests have become enormous tinder boxes filled with drought-desiccated timber - a situation worsened by overgrowth from decades of suppressing natural fire cycles necessary to maintain a healthy woodland balance.

To that end, the state enacted a sweeping plan last year to double the amount of land open to the thinning of fire-prone brush and dead and dying trees, while streamlining permits needed for landowners to clear such vegetation.

More than half of the 33 million acres (13.3 million hectares) of forest lands in California are managed by federal agencies, according to the University of California’s Division of Agriculture and Natural Resources. State and local agencies control only 3 percent, and the rest is privately owned.

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.

California plans to spend $1 billion on forest management over the next five years, the letter said, and has spent $111.3 million since 2017.