WASHINGTON (BLOOMBERG, REUTERS) - United States President Donald Trump is playing down the threat of a second partial government shutdown as Republicans in Congress clear a path for him to accept a deal on border security funding.

Mr Trump is likely to grudgingly sign the legislation and then immediately use his executive authority to fund additional border measures, said a person who talked to the President on Tuesday (Feb 12) and asked not to be identified to discuss private conversations.

Mr Trump on Tuesday expressed reservations about the agreement reached late on Monday. "I'm not happy about it. It's not doing the trick," he said during a Cabinet meeting. But he added, "I don't think you're going to see a shutdown" and said he'll consider the proposal.

He later tweeted that he had been briefed by Republican Senator Richard Shelby and was reviewing the measure.

The Republican President repeated his insistence that if Congress did not provide the funding, he would press forward with building a wall, writing: "Regardless of Wall money, it is being built as we speak!"

White House aides are considering having Mr Trump sign the compromise deal but also try to move money that has already been allocated for other programmes to instead build the wall, one official said. Mr Trump may need approval from Democrats in the House to be able to do so.

Funding for the Department of Homeland Security, the Justice Department and a host of other agencies is due to end on Saturday after the expiration of a stopgap measure that ended the longest federal shutdown in US history. Monday's tentative funding agreement would keep the government open until Sept 30, the end of the federal fiscal year.

The deal which would need to be passed by the Democratic-led House of Representatives and Republican-controlled Senate and signed by Mr Trump.

The House could vote late on Wednesday at the earliest, according to a senior aide. Congress must pass the measure by Friday's midnight deadline.

The President also said he may decide to declare a national emergency to bypass Congress to get funds for a wall - an option opposed even by many Republicans, in part because it is likely to be challenged in court.

Congressional Republicans have shown little appetite for another shutdown after taking heavy criticism over the prior one.

"I hope he'll decide to sign it," Senate Majority Leader Mitch McConnell told reporters. House Republican leader Kevin McCarthy also touted the deal.

But the most conservative members of the House are unhappy with the deal, a sign it could face trouble if some liberal Democrats also defect over border fencing funding and concerns about the number of beds in immigrant detention facilities.

"Most conservative members are having real heartburn today," Republican Representative Mark Meadows said on Fox News. "I can tell you, it's the Democrats that are walking around here on Capitol Hill with a smile on their face today, not Republicans."

'WE'RE BUILDING THE WALL'

The tentative pact reached Monday night provides US$1.375 billion (S$1.86 billion) for 88 new kilometres of border fencing in Texas' Rio Grande Valley area, according to congressional aides who spoke on condition of anonymity. That's far short of the US$5.7 billion Mr Trump wants for a wall.

But the agreement also rejects limits Democrats sought on detentions of immigrants apprehended in the US.

Mr McConnell and other Republicans said Mr Trump may be able to reprogramme other unused money in the budget to put towards his proposed wall.

"He ought to feel free to use whatever tools he can legally use to enhance his effort to secure the border, so I would not be troubled by that," said Mr McConnell of Kentucky.

Senator Roy Blunt of Missouri, a member of GOP leadership, said he is examining the federal budget for ways Mr Trump could use available funds for a wall without using an emergency declaration.

"If we get to the place where it's time to talk to the President about those, I intend to," Mr Blunt said. As an example, he pointed to a drug programme that has US$800 million in unspent funds. Other funds might be shifted from existing programmes, he said.

Senate Minority Leader Chuck Schumer said, though, that the President would need approval from Congress to move money within the budget.

"He doesn't have the authority to do it without House permission", Mr Schumer said, adding that the Democratic-controlled chamber may not agree.

Senator Susan Collins of Maine, a moderate Republican, said she is urging Mr Trump to sign the agreement and not take budget funds for the barrier without approval from Congress.

"For him to reprogramme billions of dollars without congressional approval would undermine the appropriations process and be of dubious constitutionality," Ms Collins said.

Mr McConnell said he recommended that Mr Trump wait to ensure the legislation properly reflects the agreement before announcing whether he will sign it. Mr Shelby said he expects the Bills to be introduced on Wednesday.

The agreement on the remaining seven spending Bills would keep government agencies open through the end of the fiscal year, including the Department of Homeland Security that oversees border protection.

It was a rare feat of bipartisan compromise that had seemed out of reach only 24 hours earlier. But the drawn-out struggle is sure to be revived in the next budget battle and continue into the 2020 campaigns for the White House and Congress.

Democrats dropped their demand for a cap on detention beds for immigrants detained within the US. Instead, the deal would set an average daily cap at 45,274 beds - less than the 49,057 now detained, two congressional aides said.

Democrats believe that will drop the number detained to 40,520 by Sept 30. But the aides said Mr Trump would retain authority to expand the number of beds by transferring money from other security accounts.

Mr Trump could boost the number of beds as high as 58,500 with that authority - enough to respond to a surge in illegal immigration and arrests, one aide said.

Some of the President's allies who helped convince him to hold out for wall funding last year panned the committee's negotiation almost as soon as the details were made public.

The leader of the conservative House Freedom Caucus, Mr Mark Meadows of North Carolina, said he believes Mr Trump will sign the measure and then use executive action to gain additional funds for the wall.

A key sticking point had been funding for detention beds for immigration enforcement, which Democrats wanted to limit as a way to, in effect, force Immigration and Customs Enforcement to put less of a priority on undocumented immigrants without criminal backgrounds.

One aide said the 88 new kilometres of border barrier would be double the amount of new distance provided in fiscal 2018 and nearly three times as much as would have been available if current funds had been extended through September.

The Border Patrol can use any design in current use, including steel slats, but not a purely concrete wall some of Trump's supporters have cheered.

House Democrats opened the talks with an offer of no new money for border barriers, while Senate Democrats had offered US$1.6 billion in funds before the shutdown began.

Mr Trump has been demanding a wall since the 2016 presidential campaign. The recent shutdown, the nation's longest, ended when he signed a three-week spending Bill on Jan 25 and both parties agreed to create a 17-member committee to negotiate a solution.

The President has a history of tearing up bipartisan agreements, including a potential one last year that would have provided US$25 billion in wall money in exchange for protection from deportation for young undocumented immigrants.

The deal would allow a number of departments to continue operating, including Agriculture, Commerce, Interior, Justice, State, Transportation, Treasury, and Housing and Urban Development.

The Food and Drug Administration and Environmental Protection Agency would also be funded.