CHICAGO — Forget Vancouver. The biggest question for U.S. Olympic Committee leaders these days is whether President Barack Obama will make a personal appearance at the vote to award the 2016 Games.

Obama has been a vocal supporter of Chicago's 2016 bid, videotaping four messages for International Olympic Committee members. But he has yet to say whether he'll travel to Copenhagen, Denmark, ahead of the Oct. 2 vote. Chicago is in a tight race with Rio de Janeiro, Madrid and Tokyo, and the presence of world leaders has been instrumental in the most recent votes.

Tony Blair's presence in Singapore in 2005 was key in London getting the 2012 Games, and Vladimir Putin traveled to Guatemala City in 2007 to push Sochi's winning bid for the 2014 Winter Games.

"I don't know how many ways I can answer this. I think it would be significant, extremely important, and we all hope he can join us there to enhance the Chicago 2016 bid," USOC chairman Larry Probst said Thursday after being asked yet another question about Obama at the Vancouver media summit.

Brazil's president Luiz Inacio Lula da Silva already has said he'll be in Copenhagen, as will King Juan Carlos of Spain. Japan has invited incoming Prime Minister Yukio Hatoyama and Crown Prince Naruhito to attend.

White House officials said Wednesday that Obama and Chicago 2016 will host Olympic athletes at the White House next week. The athletes will visit local schools first, then join Obama and his wife, Michelle, at the White House in the afternoon. The White House also said Valerie Jarrett, one of Obama's top advisers, will be in Copenhagen for the vote.

Jarrett, who was once vice chair of Chicago 2016, leads the White House effort to support Chicago's bid.

USOC and Chicago 2016 officials have told the White House they think Obama's presence could be key in winning the games, and Obama himself has said he will help in any way he can. But he is also fighting for a sweeping overhaul of the health care system, what could be a signature piece of legislation for his administration.

The G-20 economic summit is also in Pittsburgh the week before the IOC vote.

"The USOC, Mayor Daley, everyone involved at 2016 — we have all very clearly communicated to the White House that we think his presence would greatly assist the bid," Probst said. "That's obviously a decision they need to make in the White House depending on his schedule and what other priorities he faces as president.

"I can't provide any update, but we sure would like to have him with us."

Asked if Obama needs to make a decision soon so Danish officials can make security arrangements, Probst smiled.

"We're talking about the president of the United States," he said. "If and when he makes the decision, the appropriate accommodations will be made."