Here are the top 10 developments in this big story:
"I am thankful for the help and support that my friend Barack Obama has extended with regard to (India's) membership of the Missile Technology Control Regime and Nuclear Suppliers Group," PM Modi said, addressing the media jointly with the US President.
PM Modi said India and the US have been "working shoulder to shoulder" and "are proud of this legacy and will continue working with each other."
India and the US have agreed to build six nuclear reactors in India - a key step in closing the first deal stemming from a US-India civil nuclear accord struck over a decade ago. The AP 1000 reactors will be built by US firm Westinghouse, a unit of Japan's Toshiba Corp.
The Nuclear Power Corporation of India Ltd and Westinghouse have confirmed that engineering and site design work for the project will begin immediately and contractual arrangements will be completed by June 2017.
Ahead of the bilateral meeting between PM Modi and President Obama, it was announced that India had cleared all hurdles to becoming a member of the Missile Technology Control Regime or MTCR, a key anti-proliferation grouping.
PM Modi has also been lobbying successfully with countries like Switzerland to gain support for its bid to join the Nuclear Suppliers group, a club of 48 countries that trade nuclear technology. The US has backed India's membership of the NSG, which will strengthen India's geopolitical clout and help it capitalise on nuclear trade and technology transfer opportunities.
"We will meet again at the G20 Summit and will fulfill the dream of climate justice,"PM Modi said, adding that they discussed issues ranging from business and technology to governance at their seventh meeting in two years.
"The key priorities are how to promote economic prosperity and alleviate poverty and promote greater opportunities for both countries," President Obama said.
Addressing American businessmen later in the day, PM Modi said that the world needs a new engine of growth, and that India is poised to play that role. A larger Indian economy has "multiple benefits" for the world, he said.
On Wednesday, PM Modi will address a joint sitting of the US Congress, his 10th address to a foreign parliament since he took office two years ago.
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