Fresh from a giant-slaying win over rival Hillary Clinton in the Democratic White House nominating race, he joked that he could put his house near Chicago's Washington Park up for rent to make a financial killing if the city wins the 2016 Summer Games.
'I have to let you know in 2016, I'll be wrapping up my second term as president,' he said in a surprise appearance at a rally celebrating Chicago's selection as a finalist for the Summer Games.
'So I can't think of a better way than to be marching into Washington Park... as President of the United States and announcing to the world, 'Let the Games begin!''
Mr Obama joked that his home is only a couple of blocks from Washington Park, the proposed site of the Games, and so he had been thinking about how much he could get for renting it out.
He is hoping to be living in the White House anyway, he said.
'I might have to rent out my house. I don't know how much it's going to be worth,' he said, firing up a wild outdoor crowd of several hundred people.
Chicago is competing with Tokyo, Madrid and Rio de Janeiro to host the Games.
Mr Obama was joined at the rally by other elected officials and dignitaries and athletes, including track and field gold medallist Jackie Joyner-Kersee.
'It is a great time to be in Chicago,' he said.
'White Sox are winning. Cubs are winning. And Chicago's going to win the 2016 Olympics and Paralympics. And your senator, he's winning, too.'
AFP, AP