WASHINGTON — President Trump threatened on Friday (March 23) to veto a US$1.3 trillion (S$1.71 trillion) spending package just hours before the government was set to shut down for lack of funds, lashing out over its failure to fund his long-promised border wall.

"I am considering a VETO of the Omnibus Spending Bill based on the fact that the 800,000 plus DACA recipients have been totally abandoned by the Democrats (not even mentioned in Bill) and the BORDER WALL, which is desperately needed for our National Defence, is not fully funded," Mr Trump posted on Twitter in a message that imperiled a sweeping bipartisan agreement brokered by congressional leaders over his objections.

He was referring partly to the fact that he failed to reach a deal with Democrats to include provisions in the spending measure that would preserve Deferred Action for Childhood Arrivals, or DACA, an Obama-era programme he rescinded last fall that allows undocumented immigrants brought to the United States as children to apply for permits to work legally and avoid deportation.

But Mr Trump's failure to secure an agreement on that issue was hardly the only one in which lawmakers defied him in approving the bill. The measure itself deals a broad rebuke to the president's vision for reordering the size and scope of government, rebuffing his efforts to gut many domestic programs even as it provided the sizable military spending increase Mr Trump wanted.

A veto would almost certainly shut down the government at midnight, just as hundreds of thousands of teenagers and adults are descending on the National Mall for a gun control march. With Congress on spring recess for two weeks starting Monday, many lawmakers had already departed Washington early Friday. Some were on their way out of the country as part of official congressional delegations overseas.

And unlike recent government shutdowns that stemmed from Congress's inability to pass spending bills, this one would be precipitated by the president alone. In 1995 and 1996, vetoes of spending bills by President Bill Clinton shuttered the government temporarily, but in those cases, Mr Clinton had the support of his party's leadership in Congress, who objected to deep cuts to Medicare and conservative policy changes inserted into the spending bills.

If President Trump vetoes the new spending bill, he will have defied Republican and Democratic leaders alike.

Sensing a political advantage, Democrats were unperturbed by the tweet. Top Democratic aides said Friday morning that they would not make concessions to Mr Trump if he chose to veto the bill.

Over the weekend, the White House offered to extend protections for about 800,000 DACA recipients for two and a half years, with no guarantee beyond that time, in exchange for US$25 billion for the border wall, according to congressional aides.

Democrats countered by saying they would agree to the full $25 billion only if the president agreed to a pathway to citizenship for a much broader population of young immigrants brought to the country illegally as children, a deal that was similar to an earlier offer from Mr Trump.

The White House rejected the Democratic offer. THE NEW YORK TIMES