WASHINGTON — Trump administration officials want the Supreme Court to help them hurry up and spend up to $2.5 billion to construct a barrier on the U.S.-Mexico border before Congress thwarts them with new spending legislation on Oct. 1.

The administration argues it needs a ruling from the Supreme Court by July 26 so it can spend money on border wall construction before the fiscal 2019 spending law lapses on Sept. 30.

It’s an argument that a federal appeals court shot down earlier this month. Challengers to the wall construction say it has never been tried before. And the Democratic-led House filed a brief Friday arguing the Supreme Court should not rush because Congress says how federal funds are spent.

In its brief, the House argues the Trump administration “will still have the funds it seeks after Sept. 30 if Congress — the only body that can decide how federal funds should be spent — decides that public money should be spent as the Administration wishes.”

The government transferred the funds at issue into a Defense Department account earlier this year, part of President Donald Trump’s plan to outmaneuver Congress by shifting around existing federal funds to build barriers along the southern border.

Trump made the moves after Congress turned down his full $5.7 billion request for construction funds in a February spending showdown that resulted in the longest partial government shutdown to date.

But a federal district court blocked that effort amid a legal challenge about whether the administration has the authority to shift funds.

The Defense Department says “the remaining unobligated funds will become unavailable” after Sept. 30, and it “will be unable to complete the projects as planned,” the Justice Department said in its application to the court.

The U.S. Court of Appeals for the 9th Circuit, in a July 3 ruling, said that argument actually illustrates the weakness in the Trump administration’s case.

“Defendants’ rush to spend this money is necessarily driven by their understanding that Congress did not appropriate requested funding for these purposes in the current budget and their expectation that Congress will not authorize that spending in the next fiscal year, either,” the 9th Circuit ruling states.

The House cited that 9th Circuit language and pointed out the funds are not lost if they are not spent during this fiscal year.

Instead, the House wrote, funds “return to the federal treasury and can be appropriated for use next year, if Congress believes that they should be spent on border wall construction.”

And the House argued the Appropriations Clause of the Constitution prevents the executive branch from spending money without statutory authority.

“Once (the Defense Department) obligates and spends these funds, there will be no way to get them back, and the constitutional injury will be irreparable,” the House wrote.

The American Civil Liberties Union, which represents the Sierra Club and other environmental groups challenging the construction spending, told the Supreme Court in a brief Friday that the deadline argument isn’t really needed.

The courts have the ability to order the funds held beyond their statutory lapse date, the ACLU wrote. And “there will be no turning back” if the justices allow the government to start construction.

The ACLU also points out the Defense Department has not taken all the steps within its own power to speed up the contracting process.

The Supreme Court, which is currently on its three-month summer recess, could decide at any time.