New Delhi, Jan 25 (IANS) India and the US Sunday announced the much-anticipated breakthrough agreement on commercial implementation of their landmark civil nuclear deal, six years after it was signed, and also entered a new strategic phase of co-production of some defence projects, as Indian Prime Minister Narendra Modi and visiting US President Barack Obama held talks marked by much warmth and camaraderie.

Both Obama and Modi announced that the "breakthrough" had been arrived at in the civil nuclear deal - which ended decades of India's nuclear isolation because of its refusal to sign the Nuclear Nonproliferation Treaty (NPT) - during the joint press interaction after a marathon over three-hour talks at the Hyderabad House.

Modi said in his speech: "I am pleased that six years after we signed our bilateral agreement, we are moving towards commercial cooperation, consistent with our law, our international legal obligations, and technical and commercial viability."

Obama, describing it as a "breakthrough understanding", said the two leaders agreed to "advance our civil nuclear cooperation and we are committed to moving toward full implementation".

"It is an important step and shows us how we can work together to elevate our relationship."

"The deal is done... We have broken the logjam of the past few years," said Foreign Secretary Sujatha Singh, briefing newspersons later.

She acknowledged that the "political leadership played key role" in pushing forward the agreement.

The Indo-US nuclear contact group, that has held three meetings including one that ended in London just a day ago, had been working at a frenetic pace to tide over concerns from both sides ahead of the Modi-Obama meeting.

Sujatha Singh said there were "very specific political directions to address the concerns" on both sides.

"There is a clear intention to reinvigorate the relationship and take it forward," she said.

She also said both leaders were committed to work jointly for India's entry to the four multilateral export controls regimes - the Nuclear Suppliers Group, the Missile Technology Control Regime (MTCR), the Australia Group, and the Wassenaar Arrangement.

She said Obama "supports an early decision on India's entry into all four regimes".

In the field of defence, the two sides renewed the 10-year Defence Framework Agreement and the Defence Trade and Technology Initiative (DTTI).

The new framework is to enhance the bilateral defence partnership with more intensive joint military exercises and maritime security efforts among others.

Under the DTTI, which is for co-production, both have agreed on four projects, including the Raven unmanned aerial vehicle (UAV), and the "roll-on, roll-off" intelligence, surveillance and reconnaissance module for the Lockheed Martin-manufactured C-130 J transport aircraft, Sujatha Singh said.

Both sides are also to form a working group to explore technology for aircraft carriers and also share the design of jet engine technology.

Modi, in his opening address in English at the press interaction, said both have decided to take "our growing defence cooperation to a new level".

In the field of energy, Obama expressed interest in participating in India's 100 gigawatt solar energy project.

Both sides also resumed talks on the bilateral investment treaty and on a totalisation agreement.

"We will also resume our dialogue on bilateral investment treaty. We will also start discussions on social security agreement that is so important for the hundreds and thousands of Indians professionals working in the US," Modi said.

The two sides also inked three MoUs between the US Trade and Development Agency and the governments of Andhra Pradesh, Rajasthan and Uttar Pradesh for the smart city projects involving Ajmer, Allahabad and Vishakhapatnam.

The US is also cooperating with India on the Digital India programme.

Two-way trade which stands at $60 billion is poised to reach the $100 billion mark by 2018. The US is keen that the trade figure should reach $500 billion by 2020.

The breakthrough on the civil nuclear deal was arrived at after the India-US nuclear contact group held talks in London that were extended by a day in order to arrive at a consensus.

Besides the US' concerns over India's stringent civil nuclear liability law that puts the onus for any accident on suppliers, India had objection to the US insistence on control in perpetuity over the nuclear fuel and equipment.

The contact group was set up during Modi's US visit in September last year. It was charged with advancing the implementation of the stalled nuclear deal.

The US and India are also working towards a proposal to set up a $250 million insurance pool with money from all stakeholders to pay off any liabilities.

The insurance pool is aimed at indemnifying companies building nuclear reactors in the country, against liability in case of an accident.

In a joint statement, the two sides also elevated the bilateral relationship through their endorsement of a new India-US Delhi Declaration of Friendship, which builds on their Sep 30 Vision Statement.

Both noted commonalities in their regional policy - in India's 'Act East Policy' and the US' rebalance to Asia and said it provides "opportunities for India, the US, and other Asia-Pacific countries to work closely to strengthen regional ties".

The two also announced a Joint Strategic Vision to guide their engagement in the region.

The two leaders pledged to translate their commitment of "Chalein Saath Saath": "Forward Together We Go" of September into action through "Sanjha Prayaas; Sab Ka Vikaas": "Shared Effort; Progress For All".

Obama, who arrived in the morning, was first accorded a ceremonial welcome at Rashtrapati Bhavan after which he went to Rajghat to lay a wreath at the memorial of Mahatma Gandhi and also planted a sapling. He held marathon talks with Modi in Hyderabad House over luncheon.

The two also strolled in the green lawns of Hyderabad House without aides and had tea, with Modi pouring the tea for his VVIP guest.

The "chai pe charcha' moment drew smiles when it was referred to at the joint presser, and Obama thanked the prime minister.

Modi also said the two sides have decided to set up a hotline between the two leaders.

To a question on their body language, he referred to the US president with the first name, saying that "Barack" and he have been maintaining contact over phone, and also chat.

He said the personal equation between two leaders goes a long way towards bringing two nations and their people together.