LONDON: European shares opened broadly flat on Tuesday as investors prepared for Donald Trump's decision on whether to withdraw the US from the Iran nuclear deal, a move which could disrupt global oil supply.At 0738 GMT, the pan-European STOXX 600 index was down 0.05 per cent with a flurry of first-quarter corporate earnings and mergers and acquisitions deals prompting sharp individual price moves.Shares in Danish hearing aid maker William Demant were the worst performer, falling over 10 per cent after warning that lower demand would weigh on sales.German postal and logistics group Deutsche Post DHL also disappointed investors by missing first-quarter profit expectations and saw its shares fall 6.7 per cent.Among European blue chips, Unilever posted the best performance, up 1.9 per cent as it announced the start of a 6 billion euro share buyback scheme.In London, Shire added 2.8 per cent after Takeda Pharmaceutical said it agreed to buy the group for 45.3 billion pounds ($61.50 billion) after it raised the cash element to secure a recommendation.Sky was down 1.1 per cent after US cable operator Comcast formally notified the European Commission of its intention to bid for Britain's pay-TV group.Sources also told Reuters earlier that Comcast was asking investment banks to increase a bridge financing facility by as much as $60 billion so it could make an all-cash offer for the media assets that Twenty-First Century Fox agreed to sell to Walt Disney.