A US official has struck down security funding allotted for President Trump's White House ballroom project from a proposed spending package, in a win for Democrats.

The Senate rule-keeper ruled against the use of taxpayer funds in the bill on Saturday, after Democrats argued that security money doesn't belong in it.

Trump has said private donors will fund the $400mn ballroom as Republicans have sought to use a portion of $1bn in taxpayer funds for Secret Service security upgrades.

Republicans are seeking the funds to bolster presidential safety following a shooting at a gala Trump attended in April at a hotel. The administration also tried to fast-track the project after the incident.

Republicans, who hold the majority in the Senate, have used complex budget rules - known as the budget reconciliation process - to try to pass bills without Democratic support.

Their latest sprawling package to fund immigration agencies under the Department of Homeland Security also includes a $1bn provision for security funds dedicated to the overhaul of the East Wing of the White House, which includes Trump's plans for the ballroom.

Senate parliamentarian Elizabeth MacDonough, who has acted as a referee in the upper chamber of the US Congress since 2012, deemed the provision out of order on Saturday, Democrats said.

She determined that the provision funds activities beyond the jurisdiction of the Senate Judiciary Committee and does not comply with the Byrd rule, which prevents extraneous non-budgetary provisions.

"Republicans tried to make taxpayers foot the bill for Trump's billion-dollar ballroom. Senate Democrats fought back — and blew up their first attempt," Senate minority leader Chuck Schumer wrote on X on Saturday.

"Now Ballroom Republicans say they're going back to the drawing board to try again. And Senate Democrats will be ready to stop them again.

Schumer added: "Americans don't want a ballroom. They don't need a ballroom. And they sure as hell should not be forced to pay for one."

Senator Jeff Merkley of Oregon, the top Democrat on the committee, said that he expects Republicans to change the bill "to appease Trump" and that Democrats are prepared to challenge any changes to the bill.

"Redraft. Refine. Resubmit. None of this is abnormal during a Byrd process," Ryan Wrasse, a spokesperson for Senate Majority Leader John Thune, wrote on X.

Construction crews tore down the storied East Wing in October as Trump pushed plans for what he called the "finest ballroom of its kind, anywhere in the world".

The National Trust for Preservation has sued the administration to block further construction, arguing that the teardown and changes are unlawful without congressional approval. An appeals court ruled in April that construction of the underground and aboveground portions may continue.

The ballroom project is one of several ways that Trump, who previously worked in real estate and construction, is trying to update the US capital.

At the White House, he has added gold details to the Oval Office and paved over the presidential residence's rose garden to install a patio reminiscent of his Florida club, Mar-A-Lago.

He also retitled Washington DC institutions, such as the Kennedy Centre and Institute of Peace, to add his name and has announced plans for a 250-ft triumphal arch near the Arlington National Cemetery.