Workers rushing to finish building a metal wall between Columbus, New Mexico, in the United States, and Puerto Palomas in Chihuahua, Mexico, on Wednesday. US President Donald Trump's promise to build a wall along the US-Mexico border was the centrepiece of his immigration rhetoric during his successful 2016 campaign. More than 644km of it has been built so far, and his administration is accelerating works to complete as much of it as possible before President-elect Joe Biden takes office in January. Mr Biden's campaign had called the wall a waste of money and vowed to halt its construction.