President Barack Obama and his wife Michelle sought to inject momentum into the faltering campaign by their home city of Chicago to host the 2016 Olympic Games by staging an event for US athletes at the White House on Wednesday.

With less than three weeks before the International Olympic Committee meets in Copenhagen to elect a host city, Chicago has seen its standing as frontrunner in the four-horse race slip away, damaged by doubts about financial guarantees and wrangles between US Olympic officials and the IOC.