Senior officers of the Pakistan Air Force like to rattle off the number and types of jet fighter in India’s arsenal as proof of the deadly threat they face on their eastern border.

From the high Himalayas to the industrial city of Pune in Maharashtra, India’s largely Russian-made 400-strong fleet can strike Pakistan in as little as 15 minutes.

The days when India’s defences comprised almost entirely MiG and Sukhoi jets are drawing to an end. With many of them near obsolete, India has in the past five years turned to US weapons systems in government-to-government deals. In recent months, New Delhi has opted for Boeing’s C-130 and C-17 transport and Poseidon maritime patrol aircraft.

Now a high-stakes arms contest between European and US aerospace companies is coming to a climax as Barack Obama, the US president, prepares to visit India next month. India has a choice of F-16s or F-18 Super Hornets over Mirages, MiGs, Eurofighters and Gripens as it overhauls its aerial strike force.

A decision in favour of US weaponry would reflect a strategic shift. It was not so long ago that the US viewed India as being on the wrong side in the cold war and made it a target of punitive sanctions.

It would also be a blow to Moscow, whose arms industry has long held India’s defences in its grip, from ships and nuclear submarines to supersonic missiles and jet fighters. Since India's independence 63 years ago, Russia has provided the backbone to India's armed forces, whose 1.1m-strong army is the world’s third largest.

Buying American would highlight India’s changing assessment of threats. More and more, China's assertiveness in the region – over trade, global finance and its borders – is overshadowing the traditional and better-understood threat from nuclear-armed Pakistan.

Some senior Indian security advisers say India could face its northern neighbours on two fronts in years to come and needs to rearm urgently.

“Chinese power is radiating through the Himalayas,” says C. Raja Mohan, a senior strategic affairs analyst at Delhi’s Jawaharlal Nehru University. “This is something we have to address and deal with. . . The rise of China is going to cause a whole set of problems across Asia.”

Mr Mohan foresees the need for the US and India to work together to guarantee the freedom of “sea lanes, cyberspace and even outer space” in an alliance that has already “exploded the boundaries of south Asia”.

Others view stronger broad alliances with the US among Asian nations as a hedge against China's growing influence, and expect New Delhi to partner with Washington in regional defence and trade pacts. “The underlying economics of Asia have changed. The central strategic reality is that China has fast become the central player in economic regionalism,” says Evan Feigenbaum, adjunct senior fellow for East, Central, and South Asia at the Council on Foreign Relations.

Mr Obama is likely to follow his predecessor's example on his visit to India next month by stressing the natural alliance of two celebrated democracies.

George W. Bush, the former US president who helped transform relations between the two countries with the 2008 US-India civil nuclear agreement, was fond of describing India as a country with “one billion people and a million problems, yet still a democracy”.

Behind the broad-brush acclaim of human rights and civil freedoms, Mr Obama will nevertheless be keen to bolster this young relationship with greater defence and economic partnerships.

Some, however, doubt that what they call the two largest bureaucracies in the world – the US Pentagon and India's ministry of defence – can find common cause so easily.

One western diplomat describes New Delhi as “coquettish” in its bargain-driven approach to arms deals, and contends that any prediction about the outcome of the jet fighter competition would be premature.

She said the US could easily find itself sharing the prized jet fighter contract with France and Russia in the same way that the US-India civil nuclear programme has created opportunities for European companies.