Donald Trump Flies In To Meet Mexican President Enrique Pena Nieto

Donald Trump is in Mexico to meet the country's president, hours ahead of a much-anticipated speech in Arizona on illegal immigration.

The Republican presidential nominee talked with Enrique Pena Nieto at the presidential residence Los Pinos, before holding a joint press conference.

The Mexican president said they had had a "very open and constructive discussion" about the border and trade between the US and Mexico.

The visit is something of a surprise - not least because Mr Pena Nieto has likened the White House hopeful to Adolf Hitler and Benito Mussolini.

Mr Trump has hardly endeared himself by calling Mexican illegal immigrants rapists and criminals, vowing to build a wall along America's southern border - while billing Mexico for its construction - and threatening to tear up the North American Free Trade Agreement.

Mr Pena Nieto also invited Democratic presidential candidate Hillary Clinton, but her campaign has not yet responded.

Senior Mexican officials appeared taken aback that Mr Trump had accepted the offer.

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Mr Pena Nieto's compatriots have rained criticism upon him for asking the Manhattan real estate baron - something of a hate figure to many in Mexico - to visit.

The unpopular president, whose approval ratings had already sunk to 23%, defended his move by tweeting that he believes in dialogue to promote Mexico's interests.

But former Mexican President Vicente Fox was not so conciliatory.

"Trump not welcome in Mexico," he tweeted on Wednesday, "not by me nor the 130 millions Mexicans."

In an interview in March, Mr Pena Nieto said there was "no scenario" where Mexico would engage with the Trump wall proposal, adding that the businessman's rhetoric was damaging relations between the neighbouring nations.

Mr Trump has also stoked controversy during previous Republican rallies by accusing Mexico of sending violent offenders to the US.

Aside from this, there is confusion about what a Trump administration's policies on immigration would look like.

He alarmed some firebrand conservative allies last week when he said he was "softening" his stance on mass deportations.

There are an estimated 11 million law-abiding illegal immigrants in the US, and during recent meetings with Hispanic voters, Mr Trump's campaign manager said his stance on deportations was "to be determined".

A pledge to speedily deport illegal immigrants who commit crimes in the US is expected to feature prominently during his major speech on Wednesday evening in Arizona.