US President Donald Trump has said he is prepared for a partial shutdown of the US government – now entering its third week – to last years.

After meeting top Democrats, he also said he could declare a national emergency to bypass Congress and build a US-Mexico border wall.

Mr Trump insisted he would not sign any bill without wall funding, which Democrats adamantly oppose.

Around 800,000 federal workers have been without pay since 22 December.

The Republican president initially gave a positive account of Friday’s meeting at the White House, describing it as “very productive”.

But then he acknowledged in response to a journalist’s question that he had threatened to keep federal agencies closed for years if necessary.

“I may do it. We can call a national emergency and build it very quickly. That’s another way of doing it.”

House Speaker Nancy Pelosi said Friday’s meeting had been “contentious”.

Senate Democratic leader Chuck Schumer told reporters: “We told the president we needed the government open. He resisted.

Can Trump declare a national emergency?

Donald Trump says he can declare a “national emergency” and build his promised wall along the border without congressional approval. If that’s the case, the question becomes why he doesn’t go ahead and do that. Why put federal workers through the pain of forgoing pay and hamstring key government agencies, including the Department of Homeland Security, if he could bypass Democratic objections with the snap of his presidential fingers?

Then there’s the inevitable legal challenge from Democrats to such an exercise of presidential authority. Any presidential order to build a wall would be met by an equally imposing wall of court filings blocking its construction.

The president’s latest suggestions are best viewed as simply another attempt to gain the upper hand in negotiations with Democrats. Mr Trump says it’s not a threat – and he’s probably right. It’s a bluff.

What’s the background?

Democrats, who now hold the majority in the House, passed spending bills on Thursday to reopen the government, including $1.3bn (£1bn) of border security funds until 8 February.

But the legislation cannot take effect unless it passes the Republican-controlled Senate, where leader Mitch McConnell said his party would not back any measure without the president’s support.

The Kentucky senator called the Democratic budget “a time-wasting act of political posturing”.

Vice-President Mike Pence told Fox News the deal was being “talked about”, but that Mr Trump said no deal was possible “without a wall”.