WASHINGTON — President Donald Trump doubled down on his threat to shut down the government if he doesn't win concessions from Congress on funding for his proposed border wall and reductions in illegal and legal immigration.

But, he said, he's willing to deal.

Speaking at a White House press conference with Italian Prime Minister Giuseppe Conte Monday, Trump said the U.S. is the "laughingstock of the world" because of its immigration policy.

"I would have no problem doing a shutdown," he said. "I always leave room for negotiation, but this has been many years ... I would certainly be willing to close it down to get it done."

Asked whether that meant he had to get the full $25 billion he is seeking for a wall that he vowed would be paid for by Mexico, Trump said no.

"I have no red line," he said. "I just want great border security."

Federal spending authority will run out Oct. 1 if Congress and the president can't agree on annual appropriations bills or a short-term extension.

Neither Democrats nor Republicans on Capitol Hill have been receptive to the idea of a shutdown since Trump raised the specter of bringing the government to a halt in a weekend tweet.

I would be willing to “shut down” government if the Democrats do not give us the votes for Border Security, which includes the Wall! Must get rid of Lottery, Catch & Release etc. and finally go to system of Immigration based on MERIT! We need great people coming into our Country! — Donald J. Trump (@realDonaldTrump) July 29, 2018

Though Democrats backed down after forcing a brief interruption in government funding earlier this year, the battle line on that fight was over the president's refusal to extend Obama-era protections that prevented the deportation of people who had been brought to the country illegally as children.

This time, Trump is threatening to shut down the government if his policies aren't adopted by Congress in its spending bills. The GOP base might be energized by such a war over immigration policies, though it would put Republicans in Congress in the position of defending those policies to the broader electorate at a time when they are trying to keep control of their majorities in the House and Senate.