Washington: Sixteen US states have sued US President Donald Trump over his plan to declare a national emergency to get funding for his controversial wall along the border with Mexico, saying he has veered the country toward a constitutional crisis of his own making.

The lawsuit came after Trump on Friday declared that he would spend billions of dollars more on border barriers than Congress had granted him. The National Emergencies Act allows the President to declare a national emergency and unlock a stash of funds by invoking certain statutory authority.