Donald Trump will visit Mexico on Wednesday and meet President Enrique Peña Nieto in what could be a seminal moment in the presidential election campaign.

The Republican candidate will then return to Arizona to make a much-anticipated speech on immigration on Wednesday evening.

One of the Mr Trump's core policy pledges has been that he wants to build a wall between the US and Mexico to stop illegal immigration. He has insisted he will make Mexico pay for the wall they do not want to be built.