(Adds Chicago reaction)
WASHINGTON, Sept 11 (Reuters) - U.S. President Barack Obama is sending his wife Michelle to Copenhagen next month to urge Olympics organisers to select Chicago to host the 2016 Games.
The White House said Obama informed International Olympic Committee (IOC) President Jacques Rogge on Friday he had to stay in the United States to push his campaign for health reform.
But Obama, an enthusiastic supporter of his home town's campaign to stage the Games, promised to keep working to support the bid with his wife and his senior advisor Valerie Jarrett.
Mrs Obama and Jarrett will join U.S. organisers at the IOC meeting in Copenhagen on Oct. 2, when the host of the 2016 Summer Olympics will be chosen from the four candidate cities -- Chicago, Madrid, Rio de Janeiro and Tokyo.
"It is with great pride that I will go to Copenhagen to make the case for the United States to host the 2016 Olympics," Michelle Obama said in a statement.
"There is no doubt in my mind that Chicago would offer the world a fantastic setting for these historic Games and I hope that the Olympic torch will have the chance to burn brightly in my hometown," she said.
Mrs Obama was born and raised on the South Side of Chicago, not far from the suggested locations for the Games.
The race to host the 2016 Olympics is looming as one of the tightest yet and U.S. Olympic Committee (USOC) officials had made no secret of their belief the president could swing the vote their way.
With heads of state playing an increasingly pivotal role in the bidding process, Brazilian President Luiz Inacio Lula da Silva and Spanish King Juan Carlos have already signalled they will go to Copenhagen while Japan's new prime minister Yukio Hatoyama is expected to be in Denmark to support Tokyo efforts.
British Prime Minister Tony Blair was largely credited with helping London secure the 2012 Summer Games while the presence of Russian leader Vladimir Putin was seen as a key reason behind Sochi's successful bid for the 2014 Winter Olympics.
"I think we all understand how committed the president is to the health care plan," said Chicago bid chief Pat Ryan. "I think it is going to be well understood around the world, certainly to the IOC membership, that he would love to be there."
Chicago organisers said they do not believe the U.S. president's absence will have any negative impact on their bid.
Michelle Obama has charmed crowds in the United States and around the world and her presence will likely offer some of the spark the Chicago 2016 team is hoping for next month. Obama often jokes that his wife is the better politician and speaker.
While details of the First Lady's visit have yet to be finalised, Ryan said he expected Mrs Obama to arrive in the Danish capital in time to meet IOC members and be part of the bid's final presentation.
"We are really excited about Michelle Obama coming. The First Lady of this country is a fantastic person, she has a global image that is just tremendous," said Ryan.
"Since the beginning of the administration she has been focusing on health and sport and youth. She is committed to the young of this country so it all comes together extremely well.
"I'm very impressed with Michelle Obama and always expressed hope she would be coming to Copenhagen."
Chicago, once considered the front-runner to land the 2016 Games, has stumbled down the homestretch having been dragged into disputes between the IOC and USOC over revenue-sharing and attempts to launch an Olympic television network.
(Additional reporting by Steve Keating in Chicago; editing by Ken Ferris)
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