The Prime Minister and the US president will hold talks on Tuesday in the margins of the United Nations General Assembly meeting as the Ministry of Defence stepped up co-operation with American counterparts on the next generation of drones and autonomous systems. Officials hope the talks will build on productive phone calls between the two leaders, but Mr Burnham’s previous criticism of the president and Mr Trump’s unpredictability, his recent comments about Irish unification and hostility to UK immigration and clean energy policies make it a diplomatically awkward challenge for the Prime Minister. Donald Trump (Liam McBurney/PA)Mr Burnham said he…