"We established an ambitious new roadmap for defence industrial cooperation, which will fast track high priority co-development and co-production projects," US Secretary of Defense Lloyd Austin said as he wrapped up an overnight visit to New Delhi.

But analysts warned that such pledges needed to be backed up by concrete action.

Moscow and New Delhi have been allies for decades, with Russia by far India's biggest arms supplier.

Now India -- which has not condemned Russia for its invasion of Ukraine -- is looking to diversify, both by broadening its sources of imports and ramping up domestic production.

Western countries, including the United States and France, are negotiating multi-billion-dollar contracts, and diplomats say India is placing a high priority on technology transfer as part of any deal.

The agreement will fast-track technology cooperation and co-production in areas including air combat and land mobility systems, the "undersea domain", and intelligence, surveillance and reconnaissance, the US Defense Department said.

The initiative "aims to change the paradigm for cooperation between US and Indian defence sectors", it said, and "could provide India access to cutting-edge technologies and support India's defence modernisation plans".

India has displaced China as the world's most populous country this year, and relations between the Asian giants have been strained since a deadly high-altitude border clash in June 2020.

At the same time, Washington and Beijing are engaged in fierce competition on diplomatic, military, technological and economic fronts.

- 'Bullying and coercion' -

But India is walking a diplomatic tightrope: uniquely, it is a member of both the Shanghai Cooperation Organisation, which includes Russia and China, and the Quad, set up with the United States, Japan, and Australia to counter Beijing's growing assertiveness.

As well as arms, India also imports oil from Russia, increasing its purchases since the Ukraine war began.

Analysts said they would wait to see whether the US-India roadmap was anything more than rhetoric.

Expectations that Austin would talk about transferring engine technology to India and an armed Predator drone deal had gone unfulfilled, said Indian defence analyst Rahul Bedi.

"We've heard this many times before from respective defence secretaries, as well as the Indian side," he told AFP.

"But unless something concrete emerges I remain sceptical. The right path (of India-US relations) has to be backed with firm contracts and firm assurances."

Austin, speaking to reporters after meeting his counterpart Rajnath Singh, said boosting partnerships with India came against a backdrop of "bullying and coercion" from China, as well as Russian "aggression against Ukraine".

India's defence ministry said discussions had a "particular focus on identifying ways to strengthen industrial cooperation" with Washington, including the "co-development of new technologies and co-production of existing and new systems".

Austin's visit comes ahead of a trip by Prime Minister Narendra Modi to Washington this month.

Austin is on a tour of Asia that previously took him to Japan and Singapore, part of a push to help counter China and an increasingly bellicose North Korea.

The United States is "committed to collaborating closely with India in support of our shared vision for a free and open Indo-Pacific", Austin said.

But he added that Washington was "absolutely not trying to establish a NATO" equivalent in the region.