Barack Obama is getting down to work after his overwhelming victory in the US elections. The president-elect has until January 20 to select his senior officials and form his administration. It is thought he has already appointed Illinois representative Rahm Emanuel to be his chief-of-staff in the White House. Mr Obama will work closely with President George Bush and the Republican administration he frequently attacked on the campaign trail as US officials try to ensure a seamless handover of power over the next ten weeks. The 47-year-old Democrat, who must now resign his Senate seat, will take control of the Oval Office as America's first black president at a time when the nation is facing grave challenges at home and abroad. Mr Bush said Mr Obama would be able to count on his administration's "complete cooperation" after his "impressive victory" which he described as a "triumph of the American story". "The long campaign is now ended and we move forward as one nation," Mr Bush said. "It will be a stirring sight to watch President Obama, his wife, Michelle, and their beautiful girls step through the doors of the White House." Mr Obama announced his transition team would be headed by John Podesta, who was former President Bill Clinton's last chief of staff in the White House, along with senior campaign advisor Valerie Jarrett and Pete Rouse, Mr Obama's former chief of staff in the Senate and top campaign aide. Given the broad challenges, Mr Obama will come under pressure to quickly name his key cabinet posts including the Treasury, State and Defence departments.