President Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE on Friday threatened to veto a massive $1.3 trillion omnibus spending bill, raising the prospect of a government shutdown.

The president vented his frustration that the measure does not include enough funding for his long-promised border wall between the U.S. and Mexico or protections for young immigrants covered by the Deferred Action for Childhood Arrivals (DACA) program.

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"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 Defense, is not fully funded," Trump tweeted.

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 Defense, is not fully funded. — Donald J. Trump (@realDonaldTrump) March 23, 2018

The tweet comes after the White House reassured lawmakers that Trump would sign the spending bill, pleasing leaders in both parties who scrambled to reach a deal before Friday's funding deadline.

“Let’s cut right to the chase. Is the president going to sign the bill? The answer is yes,” White House budget director Mick Mulvaney Mick MulvaneyMick Mulvaney to start hedge fund Fauci says positive White House task force reports don't always match what he hears on the ground Bottom line MORE said Thursday.

If Trump instead vetoes the measure, it would trigger a government shutdown beginning Saturday.

Members of the House and Senate have already begun to leave Washington ahead of a two-week holiday recess and are not prepared to quickly pass a stopgap spending measure.

The Senate sent the bill to Trump’s desk early Friday morning on a bipartisan, 65-32 vote hours after the House approved the measure. The bill would fund the government through the end of September.

Sixty-five of 97 senators voted early Friday morning to approve the omnibus, giving it two-thirds support in the upper chamber and enough to override a Trump veto.

The spending package, however, would face an uphill path getting two-thirds support in the House, where Trump’s support among Republican lawmakers is more solid.

The House approved the measure Thursday with 256 out of 423 votes, or roughly three-fifths support — well short of the two-thirds threshold.

Trump had dragged his feet in supporting the proposal, even though members of his own staff had participated in the negotiations on Capitol Hill.

Speaker Paul Ryan Paul Davis RyanKenosha will be a good bellwether in 2020 At indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates MORE (R-Wis.) on Wednesday made a last-minute trip to the White House, meeting with Trump for 45 minutes to persuade the president to sign the measure.

Ryan declared victory on Thursday, telling reporters “the president supports this bill, there’s no two ways about it.”

A spokeswoman for Ryan did not immediately respond to a request for comment on Trump's veto threat.

A spokesman for Senate Majority Leader Mitch McConnell (R-Ky.) said the leader did not have a statement to issue at press time.

"One of two things will happen. He either signs the bill by the end of the day, or he ends up signing a bill he likes even less after Republicans have to renegotiate with Democrats to get out of a shutdown," the source said of the options facing Trump.

Some Republicans, however, are egging the president on.

Sen. Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (R-Tenn.) on Friday morning urged Trump to veto the measure.

"Please do, Mr. President,” he wrote on Twitter. “I am just down the street and will bring you a pen. The spending levels without any offsets are grotesque, throwing all of our children under the bus. Totally irresponsible.”

A shutdown would wreak havoc with the congressional schedule , as many lawmakers have planned official trips for the two-week Easter recess.

Sen. Christopher Coons Christopher (Chris) Andrew CoonsMurkowski: Supreme Court nominee should not be taken up before election Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE (D-Del.) is leading a congressional delegation trip to Africa, for example. And many lawmakers are in Rochester, N.Y., for the funeral of Rep. Louise Slaughter Dorothy (Louise) Louise SlaughterDemocrats must go on the offensive against voter suppression House passes bill to explicitly ban insider trading Sotomayor, Angela Davis formally inducted into National Women's Hall of Fame MORE (D-N.Y.).

Trump may be trying to highlight his reluctance to sign the bill given opposition from conservatives, who have cast it as wasteful spending. He also could be trying to skirt blame for the inability to reach a deal to protect DACA recipients, who were brought to the U.S. illegally as children.

The president floated a plan that would offer them a pathway to citizenship in exchange for funding for his border wall and changes to the legal immigration system.

But Congress rejected that proposal, instead giving Trump a fraction of the money he requested for border barriers.

“DACA was abandoned by the Democrats. Very unfair to them! Would have been tied to desperately needed Wall,” Trump tweeted minutes before his veto threat.

Updated at 10:04 a.m.

Max Greenwood contributed to this story.