Ex-Mexican president - 'We're not paying for that f***ing wall'

Former Mexican President Vincente Fox has further fuelled his Twitter war with US President Donald Trump by claiming  his country will not pay for the wall he plans to build. 

On Thursday (NZ time), Mr Trump signed two executive orders on immigration, including one that will start the building of a wall on the US southern border with Mexico. 

Construction of the wall was a key component of Mr Trump's presidential campaign. 

Mr Fox has baited Mr Trump on Twitter repeatedly, vowing that Mexico will never pay for the wall and asking if Trump is a "legitimate president."

White House press secretary Sean Spicer said the first order, signed at the Department of Homeland Security, initiates the construction of a "large physical barrier on the southern border". 

The second order addresses "sanctuary cities" and will restrict immigrants from entering the US border. 

"We're going to strip federal grant money from the sanctuary states and cities that harbour illegal immigrants," Mr Spicer said.

Construction on the wall is set to begin within a few months, although the White House has said planning to erect the barrier is already underway.