"By the year 2030, India will have the third-largest GDP in the world. China will be No. 1, the US will be No. 2 and India will be third," he said in a speech delivered at the convocation of the 125th course of the National Defence Academy at Khadakwasla near here.
"The challenge of defence forces is to defend and protect the interests of the nation that will have the third-largest GDP in 17 years. When the size (of the economy) increases, the challenge also increases," he said.
Underlining the importance of safeguarding India's access to energy supplies in the context of West Asia, he said, "Our oil import dependence will increase, especially if our growth rate and GDP go up."
Ahluwalia said "the real challenge for us is to redefine the defence challenge we face in a world which will be much more multi-polar."
India, with a GDP of USD 1.84 trillion, was ranked the 10th-largest economy in 2012, according to the World Bank. The US, at USD 15.6 trillion, is the largest economy.