President Donald Trump has said he would "love to see" the US government shut down if Congress does not agree an immigration deal.
"If we don't change it let's have a shutdown. We'll do a shutdown, and it's worth it for our country," he said.
Earlier in the day, his chief of staff said Mr Trump was unlikely to extend a deadline when legal protections for young immigrants expire.
The government briefly closed last month amid political gridlock.
Speaking on Tuesday to a White House law enforcement panel on gang violence, Mr Trump said: "If we don't change the legislation, if we don't get rid of these loopholes where killers are allowed to come into our country and continue to kill... if we don't change it, let's have a shutdown.
"I'd love to see a shutdown if we don't get this stuff taken care of."
Democratic leader Senator Chuck Schumer said Mr Trump's comment "speaks for itself".
"We had one Trump shutdown, nobody wants another, maybe except him," the New York senator added.
But White House spokeswoman Sarah Sanders later said that Mr Trump was "not advocating for the shutdown".
The press secretary said the president instead "wants a long-term deal and he wants a deal on immigration".
A delicate dance
Analysis by Anthony Zurcher, BBC Washington
Donald Trump clearly thinks he came out on top after last month's government shutdown. Given his recent uptick in opinion polls, with Republicans rallying to his side, that's not an unrealistic conclusion.
Now he's leaning into another confrontation - unless he gets his desired immigration reforms and border security funding.
That cuts against the momentum in Congress towards more temporary funding measures and, perhaps, an agreement to provide a limited extension of protection for previously covered undocumented migrants, along with more money for border security.
If Congress succeeds in kicking the can down the road far enough, the odds decrease that the president will get his desired sweeping changes to legal immigration programmes. Democrats could make gains in November's midterm elections - particularly if Daca protection is a campaign issue - and any congressional action in 2019 could be much less to the president's liking.
Passing big-ticket legislation in an election year is always a challenge. In 2018, even the basic tasks - like approving a budget - seem a tall order.
At the moment, Democrats and Republicans in Congress are engaged in a delicate dance. The president, however, seems determined to call the tune.
Earlier in the day Mr Trump said the death of an NFL footballer by a drink driver who had entered the country illegally underscored the need for immigration reform.
Two days remain before a temporary government budget passed last month is due for renewal.
On Tuesday evening, the House of Representatives passed a bill to keep federal agencies funded until next month. That measure now goes to the Senate.
Mr Trump's remarks come as lawmakers debate a legislative plan for so-called Dreamers - undocumented people who entered the US as children.
The Republican president last year scrapped the Obama-era programme known as Deferred Action for Childhood Arrivals (Daca), which benefited Dreamers.
Mr Trump set an expiry date of 5 March and called on Congress to find a solution.
Earlier on Tuesday, White House Chief of Staff John Kelly told reporters he doubted "very much" whether the president would extend Daca if there's no deal.
Mr Kelly added that the original programme was not legal.
During an impromptu interview with US media, Mr Kelly stressed that Daca permit holders would not be a priority for deportation after the deadline passes.
He also defended Mr Trump's plan to offer permanent protections for 700,000 Daca permit holders plus 1.1 million others who could qualify.
The White House chief of staff said some of those immigrants "were too afraid to sign up, others would say were too lazy to get off their asses".
Gen. Kelly, the only people who have been “lazy” & haven’t gotten “off their ass*s” is this POTUS & GOP leaders. #Dreamers have waited for over a decade for a path to citizenship while working hard & contributing to our communities. This White House can barely keep the lights on https://t.co/1u66sxKOqn— Senator Cortez Masto (@SenCortezMasto) February 6, 2018
The Trump administration last month outlined a plan for nearly two million people to become citizens, in exchange for Congress approving $25bn (£17.6bn) for a US-Mexico border wall.
The White House on Monday rejected a bipartisan immigration plan that would extend Daca protections.
The proposal by Senators John McCain and Christopher Coons included funding for border security, but not for a wall.
Any deal on DACA that does not include STRONG border security and the desperately needed WALL is a total waste of time. March 5th is rapidly approaching and the Dems seem not to care about DACA. Make a deal!— Donald J. Trump (@realDonaldTrump) February 5, 2018
President Trump tweeted that that plan was a "waste of time".
Last month, he hinted that the protected US residency status for Dreamers could be extended.
"We want to do what's right and we're going to do what's right, and we're going to solve the Daca problem," he said at the World Economic Forum in Davos, Switzerland.