LONDON, May 29 - British Prime Minister Theresa May said there would be no way to delay a June 19 start to Brexit negotiations as she urged voters to give her a strong mandate in a national election due next week.Britons head to the polls on June 8 in a snap election called by May to boost her majority ahead of negotiations with European allies as Britain leaves the European Union, but her poll lead has fallen significantly in recent days."Those negotiations will start just 11 days after polling day and there won't be any putting it off. It won't be possible to stall it. The Europeans are ready. That's the timetable that has been set," she told supporters at an event in London.