Chicago's hopes of seeing off Rio de Janeiro's late surge in the race to host the 2016 Olympics were given a major boost today after the White House announced US president Barack Obama will travel to Copenhagen ahead of Friday's vote by the IOC.
Obama will be the first US president to take on such a direct role in an Olympic bid but the importance of his presence could be significant in a race described as one the closest ever.
Tony Blair is credited with some crucial lobbying in the build-up to London's narrow victory for 2012, and IOC president Jacques Rogge believes the 2016 contest will be decided by just a couple of votes among the 106 members.
Madrid and Tokyo are also bidding although most observers believe they are lagging behind.
Pat Ryan, chairman of the Chicago 2016 bid, said: "There is no greater expression of the support our bid enjoys, from the highest levels of government and throughout our country, than to have President Obama join us in Copenhagen for the pinnacle moment in our bid.
"We are honoured that President Obama and First Lady Michelle Obama will be with us to extend a hand of friendship on behalf of our nation and the City of Chicago as we seek to welcome the world for the 2016 Olympic and Paralympic Games."
It had originally been announced that Michelle Obama would be representing her husband, who had previously said the pressure of his health care reform campaign would keep him in the USA.
The couple, who are from Chicago, will be joined by talk show host Oprah Winfrey in Copenhagen.
Chicago mayor Richard M Daley said: "We are honoured to have two of our city's most accomplished residents leading our delegation in Copenhagen.
"Who better to share with members of the International Olympic Committee the commitment and enthusiasm Chicago has for the Olympic and Paralympic Movement than the President and First Lady."