The disease, also called amyotrophic lateral sclerosis, or ALS, attacks nerve cells and can lead to complete paralysis and death. Average life expectancy is two to five years after diagnosis, according to the ALS Association.

The challenge calls on people to post videos on social media of themselves dumping a bucket of ice water on their heads — or having someone else handle the chilly chore. They also have to publicly name others to do the same thing within 24 hours or donate $100 to the ALS Association. Many people do both.

Other well-known participants include former President George W. Bush, New Jersey Gov. Chris Christie and Ethel Kennedy. The 86-year-old Kennedy family matriarch tagged Obama to participate after recently dousing herself at her family's Massachusetts estate, knowing that the president would be nearby on vacation.

Obama participated financially by donating an undisclosed sum, the White House said.

"This is all about awareness. We appreciate him donating to the cause," ALS Association spokeswoman Carrie Munk said.

Singer Justin Bieber also nominated Obama to take the challenge, which has been a boon to the advocacy group. The association said it had received $41.8 million in donations as of Thursday, compared with $2.1 million between July 29 and Aug. 21 last year.

Obama isn't the only U.S. government official who is unlikely to participate.

The State Department has banned participation by U.S. ambassadors and other high-profile foreign service officers. Department lawyers say participation would violate federal ethics rules barring officials from using public office for private gain "no matter how worthy the cause," according to an unclassified cable sent earlier this week that was obtained Thursday by The Associated Press.

Vice President Joe Biden also donated an undisclosed amount to the cause, his office said Thursday, after he was challenged by actress Julia Louis-Dreyfus, who plays a U.S. vice president on the HBO TV series "Veep."