President Donald Trump has refused to compromise on his demand for a wall to be built on the Mexican border, the cause of a partial government shutdown. He said he did not think he would have to reduce the $5.6bn (£4.4bn) in funds he was demanding and repeated a threat to declare a national emergency. His new chief of staff Mick Mulvaney said earlier he expected the shutdown to "drag on a lot longer". Democrats refuse to back the funding, calling the wall "immoral". Talks to end the partial shutdown will resume later on Sunday, with the stalemate now in its third week, affecting some 800,000 federal workers. #ShutdownStories: The impact of the government shutdownHow women are changing the face of CongressThe wall was one of Mr Trump's key campaign pledges and he had said Mexico would pay for it, something Mexico has never agreed to. What has Mr Trump said?He was speaking as he left the White House for Camp David, where he will discuss policy issues with aides. "We have to build the wall," he said. "It's about safety, it's about security for our country... We have no choice... it's a very important battle to win." Mr Trump said he thought the Democrats "want a deal", adding: "The shutdown could end tomorrow or go on a long time. It really depends on the Democrats." But he also repeated an earlier threat to declare a national emergency "depending on what happens in the next few days". US law allows him to direct military construction projects under those circumstances but the money would have to come from defence department funds and there would inevitably be legal challenges by the Democrats that would drag out the matter. Mr Trump also repeated the idea of building the wall out of "steel instead of concrete", presumably in the hope that Democrats could then claim it was not a wall. The idea has not gained traction with the Democrats so far. Mr Mulvaney told NBC's Meet the Press on Sunday that he thought the controversy was "going to drag on a lot longer. I think that's... by intention". He did not elaborate. The talks between the Democrats and Republicans on the shutdown will resume on Sunday afternoon. AFP.