U.S. President Donald Trump and senior Democrats failed to strike a deal in talks on Friday to end a partial shutdown of the U.S. government as they again fought over Trump's request for over $5 billion to fund his signature wall on the Mexican border.

After Democratic congressional leaders turned Trump down at a meeting in the White House Situation Room, the Republican president threatened to take the controversial step of using emergency powers to build the wall without approval from Congress.

Trump is withholding his support for a bill that would fully fund the government until he secures the money for the wall. As a result around 800,000 public workers have been unpaid, with about a quarter of the federal government closed for two weeks.