Moscow, Dec. 24: India and Russia today inked the single biggest deal for joint development of defence equipment New Delhi has witnessed since Prime Minister Narendra Modi came to power promising domestic military manufacture as a key component of his strategic policy.

The intergovernmental agreement on the manufacture of Ka-226T Kamov helicopters, coupled with a similar pact in nuclear energy, also helped offer at least a veneer of growth in the India-Russia economic relationship that both Modi and Russian President Vladimir Putin admitted today was a concern.

The two deals don't mean that Russian-designed helicopters will be made in India any time very soon, or that Moscow will allow components manufactured by Indian firms to run its nuclear reactors just yet.

But they capture a desperate desire on both sides to inject a fresh energy to strategic sectors where Russia traditionally hogged the Indian market, yet has had to compete in recent years with the West.

"The intergovernmental agreement on manufacture of Kamov 226 helicopter in India is the first project for a major defence platform under the Make in India mission," Modi said after a three-hour-long series of meetings with Putin and Russian officials at the Kremlin today. "It is rightly with our most important defence partner."

India and Russia, despite a relationship that both sides describe as an all-weather friendship, share trade less than New Delhi's business with Seoul. Today, Putin referred to the 14 per cent drop in bilateral trade over just the past six months, even though both the Russian President and Modi have stressed on this component of their ties since they met in July last year in Brazil.

"Some of this is because of external concerns, factors outside our control," Putin told a gathering of top Indian and Russian CEOs. "But there's no doubt we need to diversify our trade."

Diamonds, chemicals, fertilisers and heavy equipment are among the sectors the two nations identified for potential trade and investment expansion.

But today, it was the familiar pillars of the strategic and economic relationship that propped up the India-Russia partnership.

Indian companies have for years now been increasing their investments in Russia's oil and gas sector. Today, Essar completed the process of selling 49 per cent of stock it held in a Russian field to Russian oil and gas major Rosneft. Russian giant Gazprom agreed, in a separate deal, to a long-term supply of liquefied natural gas to India. Public sector Indian firm ONGC picked up a 15 per cent stake in Russia's second-largest oil field.

New Delhi inked a key pact with Moscow that will give Indian firms access to Russia's continental shelf in the Arctic Ocean for exploring and hunting for minerals, oil and gas.

It was however the Kamov helicopter deal and a nuclear agreement that will most reassure Russia that India remains committed to a defence partnership it once depended on.

"For the Russians, the nuclear and defence partnership with India remains a bedrock of the relationship," Russia expert and retired diplomat Ashok Sajjanhar told The Telegraph from New Delhi.

Modi committed a site in Andhra Pradesh to Putin for nuclear reactors earlier meant for Haripur in West Bengal, senior Indian officials confirmed. But the site wasn't named publicly - yet - to avoid a repeat of the protests that derailed the Haripur project, even before details are finalised.

A pact on "localisation" of nuclear components means that Russia will slowly transfer technology to Indian firms to manufacture parts of nuclear reactors domestically. But a joint team is yet to decide the speed of the technology transfer or the monitoring mechanisms Russia is likely to demand.

Similarly, the helicopter pact will now be followed by a joint venture the two sides will set up to decide the modalities of Russia's technology transfer. India does not have the ability to manufacture the Kamov helicopters today, or anytime in the near future, officials cautioned.

But the speed of conclusion of the deal itself is rare given India's tardy record of long delays in finalising defence projects.

"Think about, this Kamov project was discussed first just a year back when President Putin visited India," foreign secretary S Jaishankar said. "And in one year, it's done."