Donald Trump threatens government shutdown if he doesn't get wall funding

President Donald Trump on Sunday threatened to shut down the government if Democrats refuse to back Republican demands to fund a border wall with Mexico.

Mr Trump has endured a series of setbacks in his efforts to tighten the US immigration system and deliver on his election pledge to build a wall along the southern border.

His morning tweet represents a huge gamble. By tying the issue to funding the whole of government, which must be agreed by September 30, he risks a political showdown just ahead of November’s crucial midterm elections.

“I would be willing to ‘shut down’ government if the Democrats do not give us the votes for Border Security, which includes the Wall!” he wrote. "Must get rid of Lottery, Catch & Release etc and finally go to system of Immigration based on MERIT! “We need great people coming into our Country!”

His comments stand in contrast to his own leaders in the House and Senate who both previously signalled the issue would have to wait until after the midterms.

He made the same promise to close the government last year if his wall was blocked only to subsequently back down.

Funding for the border wall so far falls far short of the $21 billion the Department of Homeland Security says it would cost, although Democratic estimates put the price as high as $70 billion.

Mr Trump has also repeatedly demanded an end to the visa lottery programme, which allocates 50,000 green cards to applicants at random, and to move away from a system that prioritises visas for people with relatives in the US.

But last month a Republican immigration bill failed to make it through Congress.

At a glance | Donald Trump’s border wall

And Democratic opposition has hardened since earlier this year when party leaders suggested they would be willing to vote for $25 billion of wall funding in return for offering citizenship for young, undocumented immigrants known as Dreamers.

Meanwhile, Republicans this month unveiled a spending bill that would provide $5 billion next year to build Mr Trump's wall.

It faces considerable hurdles in the Senate, where Mr Trump’s party has a wafer thin majority and would need the support of 10 Democrats to pass the bill.

Analysts suggested Mr Trump’s brinkmanship might be designed to mobilise his base ahead of the November vote, while Democrats said shutting down government would only help their chances of picking up seats.

Republicans sounded as if they had been blindsided by the threat.

Ron Johnson, the Republican chairman of the Senate Homeland Security committee, said it would not be helpful for party hopes in the midterms.

“So let’s try to avoid it,” he told CBS's Face the Nation.

Steve Stivers, chairman of the National Republican Congressional Committee, said he didn't believe the shutdown would happen.

“I think we’re going to make sure we keep the government open, but we’re going to get better policies on immigration," he said on ABC’s This Week.