Barack Obama delivered his first press conference as president-elect yesterday in the same style he ran his campaign: cool, measured, serious and lightened by dry humour. But he made no attempt to play down the scale of economic challenges that await when he takes office in January.

"We are facing the greatest economic challenge of our lifetime, and we're going to have to act swiftly to resolve it," he said. "I'm going to confront this economic crisis head-on by taking all necessary steps to ease the credit crisis, help hard-working families and restore growth and prosperity." He calmly fielded questions on issues from the economy to Iran during the 20-minute session in Chicago but stressed that the US had only "one president at a time" and that his turn did not start until January 20.