President Donald Trump is proposing immediate budget cuts of $US18 billion ($A24 billion) from programs like medical research, infrastructure and community grants so US taxpayers, not Mexico, can cover the down payment on his border wall.
The White House documents were submitted to Congress amid negotiations over a catchall spending bill that would avert a partial government shutdown at the end of next month.
The package would wrap up $US1.1 ($A1.4) trillion in unfinished spending bills and address the Trump administration's request for an immediate $US30 billion ($A39 billion) in additional Pentagon spending.
The latest Trump proposal would eliminate $US1.2 billion ($A1.6 billion) in National Institutes of Health research grants, a favourite of both parties.
The community development block grant program, also popular, would be halved, amounting to a cut of $US1.5 billion ($A2.0 billion), and Trump would strip $US500 million ($A655 million) from a popular grant program for transportation projects.
Like Trump's 2018 proposed budget, which was panned by both Democrats and Republicans earlier this month, the proposals have little chance of being enacted.
But they could create bad political optics for the struggling Trump White House, since the administration asked earlier for $US3 billion ($A3.9 billion) to pay for the Trump's controversial US-Mexico border wall and other immigration enforcement plans.
During the campaign, Trump repeatedly promised Mexico would pay for the wall, a claim the country has disputed.
"The administration is asking the American taxpayer to cover the cost of a wall - unneeded, ineffective, absurdly expensive - that Mexico was supposed to pay for, and he is cutting programs vital to the middle class to get that done," said Senate Minority Leader Chuck Schumer.
"Build the wall or repair or build a bridge or tunnel or road in your community? What's the choice?"
Watch: Democrat Senate Minority Leader Chuck Schumer slams Donald Trump's wall funding plan
Senate Republicans are considering backing away from a showdown with Democrats over whether to fund Trump's request for immediate funding to build a wall along the US-Mexico border.
Senate Democrats have threatened to filibuster any provision providing money for the wall. And many Republicans aren't very enthusiastic about the proposal, saying the White House hasn't given them many specifics to go on.
"I'd like to hear the details. What is this wall?" asked Republican Senator John McCain.
Asked about including border wall financing in the broader spending package, Republican senator Roy Blunt, a key negotiator, said: "They will not pass together. That's just my view."
The government would shut down except for some functions at midnight April 28 without successful action on spending.
GOP leaders are eager to avoid a politically damaging shutdown, especially in the wake of last week's embarrassing failure to pass the Trump bill to repeal and replace former President Barack Obama's health care law.
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