Ambassador Zalmay Khalilzad welcoming Donald Trump to stage
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Ex-official: Trump policy speech signals shift to 'mainstream'

Republican front-runner Donald Trump delivered a policy speech in Washington on Wednesday that took on a more straightforward tone than some of his previous comments on the campaign trail.

While touching on issues such as the fight against terrorism, the Iran nuclear deal, and America's relationship with its allies, he held back from repeating some of his more controversial policy positions.

It came after a night in which he swept the board in five more primary contests, putting him well ahead of his rivals for the Republican nomination.

Former US Ambassador to the United Nations Zalmay Khalilzad, who is also author of the new book Envoy, presided over Donald Trump's speech. He spoke to the BBC's Laura Trevelyan.

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