President Donald Trump's effort to end a scheme shielding young immigrants from deportation faced an uncertain future Monday, after the US Supreme Court declined to hear the case.
Trump's move to end protections for hundreds of thousands of people brought illegally to the United States as children has been blocked by the lower courts.
The White House had urged the Supreme Court to end the deadlock, but on Monday it declined, at least for now.
The decision muddies an already complex political debate over reforms to the US immigration system.
Trump has tried to use the prospect of reinstating the program for political leverage -- a quid-pro-quo in exchange for Democrats agreeing to build his much-vaunted border wall.
Barring Supreme Court intervention the Obama-era "DACA" -- Deferred Action for Childhood Arrivals -- program will stay in place, even if recipients are still in legal limbo.
The White House on Monday insisted that the policy was "clearly unlawful."
Lower courts have disagreed, ruling that the Trump administration had ended it unlawfully.
"The district judge's decision to unilaterally re-impose a program that Congress had explicitly and repeatedly rejected is a usurpation of legislative authority," White House spokesman Raj Shah said in a statement.
"We look forward to having this case expeditiously heard by the appeals court and, if necessary, the Supreme Court, where we fully expect to prevail."
Democrats welcomed the Supreme Court's decision but said a political fix was still needed.
"Today's decision puts a little more time on the clock," said Senator Richard Blumenthal. "But fails to solve the underlying problem and in no way diminishes the urgency of Congress taking immediate action."
Some 690,000 Dreamers who registered under DACA -- plus 1.1 million others who were eligible but did not sign up -- had faced deportation beginning next month if no deal is reached.
Trump on Monday complained about the lower court decision and said "we'll see what happens."