US President George W. Bush has warned rising oil prices will mean a "tough summer" for US consumers as the high cost of gasoline (petrol) showed signs of becoming a big political issue. But even as more Americans expressed discontent over the price of filling up their gas tanks, Bush suggested there was little his government could do in the short term about the problem. "We're going to have a tough summer because people are beginning to drive now during tight supply," Bush said as he toured a California facility developing hydrogen-powered vehicles. "The American people have got to understand...