US President Donald Trump's administration has asked the Supreme Court to let it withhold more than $4 billion (£3 billion) in foreign aid.
The administration is seeking an emergency order as it tries to claw back funds for foreign assistance programs that have already been allocated by Congress.
A lower court last week said the Trump administration had a statutory obligation to spend the money, and an appeals court declined late last week to freeze that ruling.
The president attempted to use a seldom-used legislative tool to withdraw the funds. Since returning to the White House, Trump has canceled billions of dollars in foreign aid that he claims do not align with his administration's objectives.
Solicitor General D John Sauer said in Monday's filing that the lower court's injunction raises a grave and urgent threat to the separation of powers.
The President can hardly speak with one voice in foreign affairs or in dealings with Congress when the district court is forcing the Executive Branch to advocate against its own objectives, Sauer wrote.
The Supreme Court could rule at any time.
Last week, Judge Amir Ali ruled the US government had to spend the allocated money unless Congress voted to approve the Trump administration's request.
On August 28, Trump notified the House of Representatives that the administration would not spend billions in foreign aid allocated by Congress earlier this year.
Those funds include approximately $3 billion for the US Agency for International Development (USAID), alongside other aid for the State Department and international peacekeeping.
Trump, a Republican, has largely dismantled USAID, the primary foreign aid agency, due to claims of wastefulness.
To revoke the foreign aid money, he cited a so-called pocket rescission through the Impoundment Control Act, which allows a US president to request the cancellation of funds approved by Congress.
This late notice in the fiscal year means the money may go unspent, as Congress does not have enough time to act on the request.
A group of nonprofits and businesses that rely on foreign assistance funding has filed a legal challenge against this move.
It marks the first such unilateral claw back by a president in nearly half a century.
Previously, the Trump administration announced plans to spend approximately $6.5 billion in funds appropriated for foreign aid following multiple lawsuits from aid organizations.
This is not the first instance of a judicial dispute over foreign aid funding reaching the Supreme Court; earlier this year, justices rejected a request from the president to keep $2 billion in foreign aid frozen while the case progressed, resulting in a narrow 5-4 ruling.