India and the US have signed a military agreement on sharing sensitive satellite data amid Delhi's tense border standoff with Beijing.
Access to such data is considered vital for hitting missiles, drones and other targets with precision.
The deal was announced after the annual "2+2" high-level talks in Delhi on Tuesday.
Experts say the strengthening of India-US ties is aimed at countering China's influence in the region.
US Defence Secretary Mark Esper held talks with his Indian counterpart Rajnath Singh. US Secretary of State Mike Pompeo also met Indian Foreign Minister S Jaishankar.
"Over [the] last two decades, our bilateral relationship has grown steadily in its substance, facets and significance," Mr Jaishankar said on Tuesday. He added that the talks would enable the two countries to "engage much more intensively on matters of national security".
The Basic Exchange and Cooperation Agreement on Geospatial Cooperation, or BECA, is among the few deals that the US signs with close partners. It allows India access to a range of sensitive geospatial and aeronautical data that is crucial for military action.
The two sides also signed a clutch of other deals in the fields of nuclear energy, earth sciences and alternative medicine. But BECA is the most significant deal among them.
It will allow the US to "provide advanced navigational aids and avionics on US-supplied aircraft to India", an Indian defence source told Reuters news agency - that also means the US can fit high-end navigational equipment in the aircraft it supplies to India.
Twenty Indian soldiers died in a clash that erupted between troops on both sides in June, sparking months-long rounds of diplomatic talks to ease tensions. But that has not helped to de-escalate hostilities so far.
Relations between the US and China have also soured in recent months with President Donald Trump's repeated criticism of Beijing's handling of the coronavirus pandemic. The US has also rebuked China for imposing a new security law in Hong Kong, following large-scale protests.
The deal is another step forward in deepening India-US military ties. India is one of the word's biggest defence equipment buyers, but around 60-70% of its inventory is supplied by Russia.
Rajini Vaidyanathan , BBC News, Delhi
In sign of the times, hand sanitiser stations were placed in front of the press cordon, and everyone, including the politicians, were wearing a mask.
That two of America's most senior Cabinet ministers chose to travel in person to meet their counterparts during times of Covid, and a week before the US presidential vote, is an indication of just how important these talks were.
Countering the influence of China in the region is the overarching theme of this trip - US officials will also travel to Sri Lanka, the Maldives and Indonesia in the coming days - nations which enjoy strong ties with Beijing.
The US wants to change this and has become one of the fastest-growing defence suppliers for India in recent years. Echoes of such plans can be heard in the statements of both countries' leaders.
This visit will reinforce US and India's "commitment to deepening military-to-military co-operation," an official statement said after Mr Esper met Mr Singh on Monday.
"Our talks today were fruitful, aimed at further deepening defence co-operation in a wide range of areas," Mr Singh later tweeted.
This is the third round of the "two-plus-two" annual dialogue between India and the US.
The first one was held in Delhi in 2018. The latest one, originally scheduled for earlier this year, was delayed due to the pandemic and comes just a week shy of US election results. Analysts say that the timing is significant and highlights India as a priority for the US.
A tight diplomatic rope
Vikas Pandey, BBC News, Delhi
The deal is key, given the current geopolitical scenario. The US seems to have sensed an opportunity in the India-China border standoff and wants to further raise its profile in the region.
It's being seen as a signal to China that Washington considers Delhi a close military ally. And this is likely to bolster the Trump administration's anti-China rhetoric.
But Indian officials will have to walk a tight diplomatic rope.
Delhi continues to hold military-level talks with Beijing to de-escalate the situation at the border and a peaceful resolution is in its best interest. It will not want a conflict, even a limited one, at a time when it's fighting a long-haul battle against the pandemic.
This was evident from the statements made by the leaders of the two countries at a joint press conference on Tuesday.
While Mr Singh and Mr Jaishankar did not directly mention China in their statements, both Mr Esper and Mr Pompeo took swipes at China.
India will also be mindful of its relations with Russia. So it will be interesting to see how it balances its military and strategic ties with both Washington and Moscow.