WASHINGTON (AFP) - Former president George W. Bush took the so-called Ice Bucket Challenge in support of Lou Gehrig's disease research on Wednesday, and challenged his Democratic predecessor Bill Clinton to do the same.

"To you all that challenged me, I do not think it's presidential for me to be splashed with ice water," Bush said while sitting on a sunny porch dressed in a T-shirt.

"So I'm simply gonna write you a cheque," he added in a video posted on YouTube.

His wife Laura then appeared and doused Bush in icy cold war. The former president, who served from 2001 to 2009, let out a loud "oww" in shock and pain.

"That cheque is from me, I don't wanna ruin my hairstyle," Laura Bush said, bucket in hand.

And Bush then nominated Clinton to be next. "Yesterday was Bill's birthday and my gift to Bill is a bucket of cold water," the former Republican president said.

Bush's successor President Barack Obama has declined a dare from Ethel Kennedy, the 86-year-old widow of late senator Robert F. Kennedy. Obama promised to make a gift instead.

Steven Spielberg, Justin Bieber, Bill Gates, Mark Zuckerberg, Oprah Winfrey and David Beckham are among the hundreds of celebrities to have recently taken the ALS Ice Bucket Challenge, which has expanded beyond the United States across the world.

Since June, several thousand people worldwide have recorded themselves getting drenched, then posted the stunt online and challenged others to do the same, or pledge US$100 (S$125) to ALS research.

Many have done both, in an effort has raise millions of dollars for the ALS Association, which combats amyotrophic lateral sclerosis, also known as Lou Gehrig's disease.

Some 30,000 Americans have ALS, which attacks the nervous system and eventually leaves victims paralysed.

On Wednesday, the ALS Association said it had already collected US$31.5 million from July 29 to Aug 20, a huge jump from just US$1.9 million last year.