WASHINGTON, United States (AFP) — President Donald Trump reversed himself yesterday, saying he would hold back from declaring a national emergency to bypass Congress and fund his controversial plan to wall off the US-Mexican border.

Trump’s fight with Democrats over their refusal to approve US$5.7 billion for the wall project has paralysed Washington, with the president retaliating by refusing to sign off on budgets for swaths of government departments unrelated to the row.

As a result, 800,000 federal employees, including FBI agents, air traffic controllers and museum staff, did not receive pay cheques yesterday.

The three-week Government shutdown was on the verge of becoming the longest on record: at midnight on Friday it will overtake the 21-day record set in 1995-1996 under President Bill Clinton.

But despite a stream of hints that he would imminently declare a national emergency and attempt to go around Congress, Trump told a White House meeting with state and local officials: “I’m not going to do it so fast.”

Trump described an emergency declaration as the “easy way out” and said Congress had to step up to the responsibility of approving the US$5.7 billion.

“If they can’t do it…, I will declare a national emergency. I have the absolute right,” he insisted.

Until now, Trump had suggested numerous times that he was getting closer to taking the controversial decision.

Only minutes earlier, powerful Republican ally Senator Lindsey Graham tweeted after talks with Trump: “Mr President, Declare a national emergency NOW.”

It was not clear what made Trump change course.

But Trump himself acknowledged in the White House meeting that an attempt to claim emergency powers would likely end up in legal battles going all the way to the Supreme Court.

Opponents say that a unilateral move by the president over the sensitive border issue would be constitutional overreach and set a dangerous precedent in similar controversies.

The stand-off has turned into a test of political ego, particularly for Trump, who came into office boasting of his deal-making powers and making an aggressive border policy the keystone of his nationalist agenda.

Democrats, meanwhile, seem determined at all costs to prevent a president who relishes campaign rally chants of “build the wall!” from getting a win.

Both Democrats and Republicans agree that the US-Mexican frontier presents major challenges, ranging from the hyper-violent Mexican drug trade to the plight of asylum seekers and poor migrants seeking new lives in the world’s richest country.

There’s also little debate that border walls are needed: About a third of the frontier is already fenced off.

But Trump has turned his single-minded push for more walls into a political crusade seen by opponents as a stunt to stoke xenophobia in his right wing voter base, while wilfully ignoring the border’s complex realities.

For Trump, who visited the Texas border with Mexico on Thursday, the border situation amounts to an invasion by criminals that can only be solved by more walls.