SUNDAY TIMES WEB DESK: Declaring a national emergency without legitimate cause could create a constitutional crisis,” James said in a statement.

“This action will harm Americans across the country by diverting funds necessary to handle real emergencies and real disasters to advance the president’s personal agenda,” she added.

“We will not stand for this abuse of power and will fight back with every legal tool at our disposal.”

Trump said Friday he expects to be sued over his decision to deploy his emergency powers to build the wall, using billions of dollars in federal funds allocated for other purposes.

Trump said the move was necessary to stem an immigration “crisis” on the US border with Mexico.

“The courts will determine that. I expect to be sued. I shouldn’t be sued,” he said at the White House.

“Sadly it will go through a process and happily, we’ll win. I think,” he said.

Legal experts and Democratic opponents in Congress say Trump is stretching his legal authorities and the definition of “emergency”.

“It would be hard to imagine a weaker case for a national emergency than this one,” said Democratic Representative Adam Schiff.

“I am confident the courts will sternly rebuke this declaration, by swiftly upholding the lawsuits which are sure to challenge today’s action.”