President Enrique Pena Nieto has also invited Democratic presidential hopeful Hillary Clinton for talks in Mexico. Donald Trump will travel to Mexico later to meet the country’s president, hours ahead of a much-anticipated speech on illegal immigration.

“I have accepted the invitation of President Enrique Pena Nieto, of Mexico, and look very much forward to meeting him tomorrow,” Mr Trump posted on Twitter late on Tuesday.

The Republican presidential nominee’s visit is something of a surprise move – not least because Mr Pena Nieto has likened the candidate to Adolf Hitler and Benito Mussolini.

Most of Mr Trump’s rallies have centred on his controversial pledge to build a wall along America’s southern border with Mexico to prevent illegal crossings – and make Mexico pay for its construction.

In an interview in March, Mr Pena Nieto said there was “no scenario” where Mexico would engage with such a policy – adding Mr Trump’s rhetoric was damaging relations between Mexico and the US.

Mr Trump has also stoked controversy during previous Republican rallies by accusing Mexico of sending violent offenders to the US and labelling Mexican migrants as drug-runners and rapists.

Aside from this, there is confusion about what a Trump administration’s policies on immigration would look like, and he worried some 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 in Arizona.

Details of the encounter between Mr Pena Nieto and Mr Trump are still being finalised, according to a spokesman for the Mexican president.