LONDON (Reuters) - Polio can be stopped in all but one place within three years, billionaire philanthropist Bill Gates said on Monday, adding that he would step up his investment in a global plan to eradicate the crippling disease.

A Cambodian boy who suffers from polio wears prosthetics he received at the Handicap International physical rehabilitation centre in Takeo July 6, 2010. REUTERS/Damir Sagolj

In an interview with Reuters, the founder of Microsoft MSFT.O, who now has a $34 billion foundation devoted largely to health projects in poor countries, said he and other donors would announce new donations in coming weeks which should help close a $700 million funding gap in the fight against polio.

“The polio campaign requires about a billion dollars a year, and for 2011/2012, about $700 million of that is unfunded,” Gates said.

“I hope that a meaningful part of that gap is closed. We won’t get rid of it all in these next two weeks, but it would tragic if the financing was the reason this thing failed.”

Polio, which spreads in areas with poor sanitation, attacks the nervous system and can cause irreversible paralysis within hours of infection. Children under five are the most vulnerable.

Polio is endemic in just four countries -- India, Pakistan, Nigeria and Afghanistan -- and there has been a 99 percent reduction in cases since 1988, when the World Health Organization (WHO) and its partners formed the Global Polio Eradication Initiative to fight it.

At that time, polio was endemic in 125 countries and caused paralysis in nearly 1,000 children every day.

“There’s no doubt that this last part (of the fight) is the hardest ... but we’re in the endgame here,” Gates said.

“A continued commitment by the donors into those countries makes us think that, say, in three years we could be down to one place where it has never been stopped -- and then we could just focus in on that.”

Gates is traveling to Abu Dhabi later this week where he is expected to make a joint announcement with Crown Prince Sheikh Mohammed bin Zayed al-Nahayan on funds for fighting polio in Afghanistan and Pakistan.

He is expected to make a further announcement on polio funding later this week at the World Economic Forum in Davos, Switzerland.

Gates described the fight to wipe the virus out in the last few places as an “acute situation” and one that needed more funds right now. “It needs money and ... this is the best investment that can be made.”

Polio vaccines are made by several companies and the WHO has certified various types made by GlaxoSmithKline GSK.L, Novartis NOVN.VX, Sanofi-Aventis SASY.PA, Panacea Biotec PNCA.BO and others for use in its immunization campaigns.

Latest figures from the Global Polio Eradication Initiative show there were about 940 cases of polio worldwide in 2010, compared with about 1,600 globally in 2009.