Nearly every federal program has been cut off from funding with the administration to determine if it supports social issues Trump opposes.
Officials are being asked if the programs support abortion, “gender ideology”, diversity programs or lowering greenhouse gas emissions.
“The use of Federal resources to advance Marxist equity, transgenderism, and green new deal social engineering policies is a waste of taxpayer dollars that does not improve the day-to-day lives of those we serve,” acting director of the Office of Management and Budget Matthew Vaeth said.
Funding for preschool education, Meals on Wheels, school lunch programs and cancer research have been stopped.
Programs to support domestic violence victims, subsidise heating for the impoverished, and helping new mothers breastfeed have also been affected.
The funding pause has blocked the online portals for Medicaid, the federal health program for poorer Americans.
“This is a blatant attempt to rip away health insurance from millions of Americans overnight and will get people killed,” Democratic Senator Ron Wyden said.
Speaker Mike Johnson, an ally of Trump, called the freeze “an application of common sense”.
“I think these would be quick reviews,” he said.
“We want to make sure that the executive orders of the new president are being fully complied with.”
Also frozen is funding for all foreign aid programs.
Already the distribution of HIV, malaria and tuberculosis drugs in foreign countries has been halted.
The HIV program established by George W. Bush is credited with saving the lives of 25 million people.
Meanwhile, staff at the UN’s refugee agency has been ordered to not order any new supplies except for emergencies as they deal with a massive funding cut.
Illinois Governor JB Pritzker, a possible Democratic candidate for president in 2028, said Trump’s actions were “illegal”.
“I know these are challenging times, and the Trump administration is trying to confuse the American people,” he said.
“That’s why it’s so important that we speak plainly.”
Hours after the pause was announced, it was blocked by a federal judge.
Judge Loren L. AliKhan questioned whether the Trump administration was aware of the ramifications of its actions.
“It seems like the federal government currently doesn’t actually know the full extent of the programs that are going to be subject to the pause,” AliKhan said.
The White House is using a power of the president called impoundment to stop the spending.
In Pictures: Everything Trump did on his first full day in the White House
Impoundment allows a president to stop spending approved by Congress.
But legal critics say impoundment is illegal if done unilaterally or permanently.
Instead, a president is required to submit proposed cuts to Congress for approval.
This is typically only done if a federal program has come in under-budget.
Overnight, Trump wrote ten posts on his social media site, but did not mention the funding freeze.