"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.

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 putting 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 defense sectors", it said, and "could provide India access to cutting-edge technologies and support India's defense modernisation plans".

India displaced China as the world's most populous country earlier 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.

But India is walking a diplomatic tightrope: uniquely, it is a member of both the Shanghai Cooperation Organisation, which includes both 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.

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 in June.

Austin visited India as part of 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 added they were "absolutely not trying to establish a NATO" equivalent in the region.