Prime Minister Manmohan Singh [Images] on Monday told defence scientists to speed up work on advanced technologies like hypersonic propulsions, unmanned vehicles and stealth machines to keep pace with current trends in warfare.

Emphasising that the country will leave no stone unturned to ensure the requisite level of defence preparedness, Singh said keeping pace with technologies like smart materials, micro and nano technologies and robotics would enable India to contend with emergence and growth of non-conventional and asymmetric warfare.

Stressing that self-reliance and defence preparedness was not a case of numbers or percentages, the Prime Minister, addressing a Technology Day function in New Delhi, said scientists should clearly define strategic and critical areas in which development of national capability is a must.

"We must pursue this goal with determination and long term perspective," Singh said as he voiced his government's determination to broad base the defence industry in the country.

The Prime Minister's comments came after the country's top defence scientist M Natarajan said that the Defence Research and Development Organisation was facing 'definite capacity constraints'.

Natarajan said, "It is impossible for the DRDO to cater to the entire spectrum of products and services required by the army, navy and air force."

The Prime Minister said that the country's resources, infrastructure capabilities and intellectual capital -- in both public and private sectors -- should be treated as national assets and carefully nurtured and optimally utilised.