US President Donald Trump said on Friday he could use emergency powers to build a wall on the US-Mexico border without approval from Congress.A showdown between Trump and Congressional Democrats over funding for the project has led to a two-week government shutdown. Trump says he will not support a bill to fully fund the government until he secures the money for the wall.Asked at a White House press briefing whether he had considered declaring a national emergency to build the wall, Trump said: "Yes, I have. ... We can do it. I haven't done it. I may do it."