By Monica Gupta BBC correspondent in Delhi

China is enjoying an export-led boom

Helped by "robust" long-term growth, China and India will hit the top three by 2050, according to New Delhi-based think-tank RIS.

RIS said China is currently the fastest-growing region in the world, followed by South Asia.

But it added that reforms were needed to keep growth on track.

Trade pact

The think-tank said the South Asia region should forge deeper trade alliances and upgrade its skills base in order to meet the challenges ahead.

"Countries that are not part of any trade blocs face the risk of discrimination of their exports and loss of competitiveness," RIS said.

"An immediate challenge for South Asia is to expedite the move towards its own free trade agreement and further vision of deeper economic integration."

The think-tank added that the region must also move towards more high-tech manufacturing in order to boost its export earnings.

"The region needs to pay attention to innovative activity to upgrade the technology profile of exports," RIS said.

It singled out currency fluctuations, "creeping protectionism" in the developed world, and the risk of terrorism as the greatest threats to continued growth in south Asia.

The World Bank said on Tuesday that India could achieve a sustainable annual growth rate of about 8% provided it cut its fiscal deficit and pushed through urgently-needed economic reforms.