Mr Obama was previously a senator for Illinois and lived in Chicago
US President Barack Obama will travel to Copenhagen to support the bid by the city of Chicago to host the 2016 Olympic Games, the White House says.
He will join his wife, Michelle, and other administration members at the International Olympic Committee meeting in the Danish capital on Thursday.
Chicago faces opposition from Madrid, Rio de Janeiro and Tokyo in the vote.
Brazilian, Spanish and Japanese leaders are also expected to lobby IOC delegates at the meeting.
Gordon Farquhar, BBC Sport
These bids are now being run like election campaigns, by hard-nosed political strategists working out tactics for grabbing the second or even third preference votes that will be crucial to the chances of any of the bidders.
Strict IOC rules dictate the boundaries of what is permitted, and transgressing them could be fatal.
Expenses-paid trips to bid cities for voting members - with freebies ranging from the odd case of wine to dental work to scholarships for offspring - were banned after the Salt Lake City "votes for gifts" scandal.
It is all strictly above board now.
However, one of the unexpected consequences of the ban on members' visits seems to be that if you cannot go to the city, the city now comes to you, with half the nation's politicians, sports stars and famous alumni in tow.
Correspondents say the impact of star personalities on Olympic bids was demonstrated when lobbying by former UK Prime Minister Tony Blair in 2005 helped London win the 2012 Games, and Russian President Vladimir Putin led Sochi's bid for the 2014 Winter Olympics in 2007.
Brazilian President Luiz Inacio Lula da Silva expressed hope on Monday that he would "return from Copenhagen with a victory".
"This is a fight," he said in his weekly radio programme. "And if we don't win, we'll have to prepare for another one."
Mr Obama, who was senator for Illinois and lived in Chicago before his election to the White House, will be the first sitting US president to take on such a direct role in an Olympic bid.
He will be joined on Friday by Education Secretary Arne Duncan and Transportation Secretary Ray LaHood, who are both from Illinois.
"President Obama and First Lady Michelle Obama symbolise the hope, opportunity and inspiration that make Chicago great, and we are honoured to have two of our city's most accomplished residents leading our delegation in Copenhagen," Chicago Mayor Richard M Daley said on Monday.
"Who better to share with members of the International Olympic Committee the commitment and enthusiasm Chicago has for the Olympic and Paralympic Movement," he added.
Mr Obama had reportedly told IOC chief Jacques Rogge last week that the pressure of his push for healthcare reform would prevent him from attending the meeting.
The race to host the 2016 Olympics has been described as one of the closest in history.
But correspondents say Chicago, with President Obama's overt support, could be considered a slight favourite.
Chicago was chosen to bid for the Games two years ago by the US Olympic Committee ahead of four other US cities.
The city's plan revolves around providing a compact event in the middle of the city, on the shores of Lake Michigan, using many established venues. The costs of Games will be borne by the private sector - unlike the three other bids.
Other government heads will be lobbying IOC delegates in Copenhagen
It is expected that Chicago's renowned skyline, history and cultural heritage will be positive factors in its Olympics bid, while the city also boasts good transport infrastructure.
Although there is no official IOC continental rotation policy, correspondents say the Americas may have an edge as previous games will have been held in Asia, Europe, and Australasia.
This factor, they add, is considered the most significant weakness of both Madrid - one of the few major European capitals yet to host the Games - and Tokyo's bids.
Rio de Janeiro's successful staging of the Pan-American Games in 2007 and their future hosting of the 2014 World Cup seemed to bolster its prospects, but the IOC recently noted that it would not be capable of providing the level of security and safety required for the Games.