* Region's infrastructure poses threats to growth, poverty
* Up to 9.9 pct of GDP investment needed
* Almost 30 pct of population still lack electricity
NEW DELHI, April 2 (Reuters) - South Asia needs up to $2.5 trillion of investment in infrastructure by 2020 if the region is to make further gains in battling poverty and provide for its growing population, the World Bank said on Wednesday.
Despite boasting similar economic growth rates to East Asia, the region lags significantly in its population's access to water supplies, power grids and roads, and by some measures is comparable to Sub-Saharan Africa, the bank said in a new report.
"The South Asia region continues to suffer from a combination of insufficient economic growth, slow urbanisation, and huge infrastructure gaps that together could jeopardise future progress," said Luis Andres, report co-author and Lead Economist for Sustainable Development for the South Asia Region.
To bring its infrastructure up to scratch, the World Bank said the region needs to invest between 6.6 and 9.9 percent of 2010 GDP a year.
That is as much as three percentage points over the current 6.9 percent invested by the region, which includes Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan and Sri Lanka, in 2009.
South Asia has "enormous" infrastructure needs, the bank said.
More than a quarter of the population still lack access to electricity, far more than the less than 10 percent who lack it in other parts of the developing world.
The region also has the highest incidence of open defecation in the world - with 680 million people, or 41 percent of the population relying on it in 2011 - and although 90 percent of people enjoy improved water access, most of this is via public stands, with only 25 percent having access to piped water.
The bank said governments should ensure infrastructure access is extended to people who need it the most - women, the poor and marginalised groups - and move away from a "build, neglect, and rebuild" mindset by investing in the rehabilitation and maintainence of infrastructure assets. (Reporting by Tommy Wilkes; Editing by Jacqueline Wong)