INDIA could test fire its most powerful nuclear-capable missile yet as early as today, a 50-tonne, 20-metre rocket that has the potential to reach all of Asia and large parts of Europe.

The Agni V - named for the Hindu god of fire, but given the incendiary appellation ''the China Killer'' by the more sensationalist of the local press - has a range of more than 5000 kilometres, and has been slated for a 1000-second test flight some time between today and Friday.

But the rocket will likely be fired from Wheeler Island off the eastern state of Odisha this morning, if all goes to plan and the weather holds, India's Defence Research and Development Organisation said.

The launch time is flexible ''because this is our longest-range missile and there are many logistics issues and hence we don't plan for one day,'' a spokesman, Ravi Gupta, said.

''Agni V is a 5000-plus kilometre range missile and it is to meet our present-day threat perceptions, which are determined by our defence forces and other agencies,'' Mr Gupta said.

A successful test would make India just the sixth country known to deploy intercontinental ballistic missiles. Only the five permanent members of the United Nations Security Council - the US, China, Russia, the UK and France - have that capability.

While Indian officials are at pains to reiterate the country's ''no first strike policy'', India's newly muscular armoury, and the hastening pace of its development, is feeding anxieties about a regional arms race.

India was declared by the Stockholm International Peace Research Institute as the biggest arms importer in the world, spending $US12.7 billion ($12.3 billion) on hardware and weapons over the past five years.

India will increase its total defence spending by 17 per cent this year to $38.6 billion, more than four times the government's spending on health care for 1.2 billion citizens.

India sees neighbours Pakistan and China, with both of whom it has border disputes, as its greatest existential threats.

The earlier, shorter-range Agni series missiles were designed to fortify the country's border and to reach every corner of western neighbour Pakistan. But the series IV and V have been built entirely in India, with China in mind.

''This missile is about neutralising the threat coming from China,'' said Uday Bhaskar, a former commodore in the Indian navy and now an analyst at the New Delhi-based National Maritime Foundation. ''The tests are about trying to create equality with China rather than trying to outdo it.''

China and India fought a war in 1962 and still dispute massive swathes of the 3500-kilometre border they share along the Himalayan mountain range.

But China's nuclear arsenal still dwarfs India's. The Communist state is believed to have about 410 nuclear warheads to India's 70.

with agencies