Barack Obama has urged Congress to back his plans for a fiscal stimulus package to revive the US economy. The US President-elect wants to cut taxes and increase state spending by up to $775 billion (£520bn) over two years, funded in large part by increased borrowing. In a high-profile speech in Virginia, Mr Obama laid out plans to boost the alternative energy sector, expand broadband networks, rebuild schools and universities and make federal buildings more energy-efficient. He said: "I don't believe it's too late to change course, but it will be if we don't take dramatic action as soon as possible." Mr Obama warned that if Congress does not back fiscal stimulus, "a bad situation could become dramatically worse". Chancellor Alistair Darling said: "I absolutely welcome President-elect Obama's determination to take substantial action to prevent the US economic situation from getting worse. There is a growing international consensus on the best way to tackle the global economic problems."