This was far less than the US$5.7 billion Trump wanted, but it was presented as a workable deal to satisfy both sides and allow Trump to shelve his threat to shut down large portions of the government on Friday.

Trump said he would manage to “add” to the congressional funds, though he did not explain how.

Lawmakers, including from his own Republican Party, pressured Trump to take what was on the table.

Senator Richard Shelby, the top Republican negotiator, called it “a pretty good deal”.

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Democratic Senator Patrick Leahy said the compromise would be voted on and likely passed, ready for Trump’s signature.

“The deal is the way it’s going to be written, and it will be filed, I suspect, tomorrow night,” he said.

The funds would finance 88.5km (55 miles ) of new walls along the border.

Hundreds of miles of barriers already run along the US-Mexican border, but Trump says far more are needed to bring what he often calls an “invasion” of migrant criminals under control.

Democrats say Trump vastly exaggerates the crime problem and uses the issue to whip up his right-wing voter base.

In December, Trump tried to pressure Congress into approving the US$5.7 billion by refusing to sign off on funding large parts of government that have nothing to do with the wall, putting 800,000 jobs, from FBI agents to airport security, on hold for five weeks.

The Democrats refused to budge and Trump was forced into an embarrassing retreat, allowing new negotiations to open with a new deadline of this Friday.

This time, Republicans appear desperate to avoid a second shutdown, leaving Trump with less political cover.

Republican Senate Majority Leader Mitch McConnell said the compromise deal was “certainly good news”.

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“Looking over all aspects knowing that this will be hooked up with lots of money from other sources,” Trump tweeted about the deal. “Will be getting almost $23 BILLION for Border Security. Regardless of Wall money, it is being built as we speak!” he added, without providing further explanation about his figures.

Although there’s little doubt that organised Mexican drug crime and people smugglers present a threat along the US border, Trump’s fixation on wall building has polarised Americans to the point where the left and right can barely discuss the issue.

For Trump, chants of “build the wall” were crucial to his surprise 2016 election victory. At a rally in El Paso, Texas, on Monday he introduced a new slogan for his coming 2020 re-election bid: “Finish the wall.”

The thousands of devoted Trump fans, many of them wearing his red “Make America great again” campaign hats, cheered at the dire warnings about Mexican criminals and calls for bigger and longer walls.

“Walls save lives, walls save tremendous numbers of lives,” Trump told them.

There was a counter-message a short distance from where Trump spoke when rising Democratic star Beto O’Rourke – a possible challenger in 2020 – held his own rally.

“Tonight, we will meet lies and hate with the truth and a positive, inclusive, ambitious vision for the future from the US-Mexico border,” he said.