A close ally of Donald Trump said talks about the cost of building a wall with Mexico were not supposed to be part of the discussion during the Republican presidential candidate's recent meeting with Mexican President Enrique Pena Nieto.

After the two met in Mexico last Wednesday, Trump told reporters they did not discuss his demand that Mexico pay the cost for construction of a wall on the border between the two countries.

Hours later, however, Pena Nieto said on Twitter he did raise the issue of the cost of the wall.