President Donald Trump declared a State of Emergency on Friday to fund his campaign promise of building Mexico border wall, after the Congress resolutely refused to give him the money he wanted.

Trump backed away from his threat to again shut down the government if the legislature did not vote $5.7 billion for the border wall and approved the bipartisan funding bill without the allocation, and instead resorted to the Emergency.

He cited the drug-smuggling problems and the “15,000” people who came to the border in convoys from Central America and are camped there hoping to cross the frontier, as reasons for his Emergency.

Unlike in India, an Emergency of the type that Trump is planning does not bring sweeping powers or allow suspension of civil rights and arbitrary arrests, but only enables limited action in government operations.

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House Speaker Nancy Pelosi and the Democratic Party’s leader in the Senate, Chuck Schumer, declared that imposing an Emergency would be “a lawless act, a gross abuse of the power of the presidency”.

Pelosi said that challenging the Emergency in court was an option.

Announcing the Emergency at the White House, Trump said that he expected a cases to be filed in a federal court with judges favouring the Democrats which he would lose and a subsequent appeal, but would ultimately prevail in Supreme Court.

Trump also called on the Democrats to work with him on broad immigration reforms that would include ending immigration of relatives of citizens, but move towards a merit-based preference for immigrants.

Congress passed the bill on Thursday with $1.375 billion for a 55-mile fence, nowhere near the $5.7 billion Trump had demanded for the wall along the Mexican border that he had promised during his election campaign.

The measure was hammered out by lawmakers from both parties after Trump allowed the government to reopen after a 35-day shutdown in a showdown over the wall funding.

Trump had threatened to veto any bill without the money he demanded for the wall, but is now agreeing to it while making good on his threat to impose an Emergency to get money for the wall.

Calling the Emergency a “presidential over-reach” and “a dangerous precedent”, Democratic Party Representative Raja Krishnamoorthi said: “The Constitution maintains that only Congress has the power of the purse and may appropriate funds. This is not a Constitutional power any President has.”

Pelosi said a legal challenge was “an option and we’ll review our options”.

Several lawmakers from Trump’s own party were against an Emergency declaration. Republican Senator John Cornyn called it a “dangerous step”, saying: “The President is going to get sued and it won’t succeed in accomplishing his goal.”

He added that if Pelosi introduces a resolution against the Emergency, it will split the Republicans.

According to media reports quoting the White House officials, Trump plans to spend a total of $8 billion on the border barrier. While there is $1.375 billion allocated in the spending bill, he wants to make up the rest by diverting money from the military construction budget and funds seized from drug smugglers and dealers.

Trump had said during his election campaign that he would make Mexico pay for the border wall – an unrealistic claim that has continued to haunt him as he sought funding in the US budget.

While government was under a shutdown with all but the essential services operating and 800 government employees under temporary layoff, Trump scaled back his idea of a wall to a series of metal slats along the border.

Having had to back down from his funding demand with Pelosi standing firm amid growing opposition to the shutdown, Trump sees the Emergency as the only way for him to build his barrier and save his credibility among his most steadfast supporters.