Indian and Russian officials are counting on a one-on-one dinner Putin will host for Modi in the evening on June 1 for a reset in a relationship that has transformed from a committed romance to a bickering couple's struggle to appear happy in public.
Modi is in to St. Petersburg for an annual meeting with Putin amid rising differences over their approach to Afghanistan's ongoing war, and unease in New Delhi over Russia's deepening ties with Pakistan and its tighter embrace of China.
On his arrival here, Modi tweeted, "Reached the historic city of St Petersburg. Looking forward to a fruitful visit aimed at cementing India-Russia relations."
On Thursday, Modi will hold the 18th India-Russia annual bilateral summit with Russian President Vladimir Putin.
With hours to go before the summit, Indian officials told PTI that last-minute talks are taking place to iron out details and language of the agreement on a line of credit for building Unit 5 and 6 of the Kundankulam nuclear power plant in Tamil Nadu. "The agreement remains work in progress," the source said.
The reactors are being built by India's Nuclear Power Corporation of India Ltd (NPCIL) and Russia's Atom stroy export company, a subsidiary of Ros atom, the regulatory body of the Russian nuclear complex.
The two sides are expected to ink 12 agreements in wide ranging sectors, including in science and technology, railways, cultural exchanges and other business areas between private parties also, in addition to a "vision statement" that the two leaders will release.
The nuclear deal, if signed, would be the centerpiece of the summit, the second time in eight months after their last bilateral in Goa in October 2016.
If signed, the two units of the plant, with capacity to produce 1000 MW of electricity each, will significantly boost the country's nuclear power generation.
The current nuclear power generation capacity of all 22 nuclear power reactors is 6780 MW.
In October 2015, a joint statement between Modi and Putin promised the signing of a General Framework Agreement on the nuclear units by December 2016. After an inter-ministerial group cleared the project, it was sent to the Prime Minister's Office for approval. But, sources said, the Credit Protocol, or a line of credit that Russia was to provide, proved to be a hurdle.
"There is a lot of mutual trust and personal chemistry between the two leaders that has developed over the last three years," Pankaj Saran, India's ambassador to Russia," told PTI.
At the summit tomorrow, "the leaders will take stock of the current relationship and discuss a blueprint for a vision of the future," he said.
India's traditional ties with Russia dating back to the days of Soviet Union have been complicated by Moscow's growing economic and political alliances with China and Pakistan.
However, Saran said India's relations with Russia are independent of its ties with Pakistan.
"Our relations with Russia is on a different pedestal and we have a full agenda between us that is important to both of us. We have clear understanding of our core concerns and vital security interests," he said, hours before Modi was to arrive from Spain.
Putin, who has been captured in photographs grappling with cheetahs and riding horses shirtless, has hosted Modi for a private dinner once earlier, at the President's dacha - country house - on the outskirts of Moscow in December 2015. But then, relations were smooth, even if stagnant.
Since then, though, ties have hit a series of bumpy air pockets. In 2016, Russia announced its first ever-military exercises with Pakistan and went ahead with them in September despite the attack by Pakistani terrorists in Uri days earlier.
Then, in December, Russia began reaching out to the Afghan Taliban as a counter to the growing influence of the Islamic State in Afghanistan's Khorasan province. Unlike the Taliban, the IS is an expansionist force and Russia fears a spill-over of militancy into its neighbourhood. But the Taliban, supported by Pakistan's intelligence services, counts India as a key enemy.
Russia called trilateral talks on the future of peace negotiations in Afghanistan end-December, inviting Pakistan and China but not India or Afghanistan, sparking rare public criticism from both Kabul and New Delhi.
Russia has invited India -and Afghanistan - to subsequent rounds of these multilateral discussions. But it has not shunned talks with the Taliban, and has even justified them.
Earlier this month, Putin was also the star guest at Chinese President Xi Jinping's summit on the One Belt One Road (Obor) connectivity initiative that India boycotted. The Obor includes an economic corridor that passes through Pakistan-occupied Kashmir.
Modi arrived in stormy weather in St. Petersburg, the former capital of imperial Russia that was founded by Czar Peter the Great in 1703, and was also known as Petrograd and Leningrad.
The prime minister will begin his three-day Russia sojourn with a visit tomorrow to the Piskariovskoe cemetery, a memorial for some 500,000 Russians who were killed in the siege of Leningrad in World War II, which the Russians call the Great Patriotic War.
Modi will then be received by Putin at the Konstantin Palace, a sprawling regal complex that is also the Russian president?s official residence where he hosts world leaders. After the summit, Putin will host Modi at a private dinner without any aides.
On Friday, Modi will be the guest of honor at the annual St. Petersburg International Economic Forum, which is being attended by a host of political and business leaders from around the world. It's the first time that an Indian prime minister is attending the economic and business summit.
Some 60 Indian CEOs are attending the summit, and India has also set up a Make in India pavilion in addition to hosting round-tables and an exclusive India-Eurasia economic and business breakfast.
Trade between the two nations stands at USD 7.8 billion, down from USD 10 billion in 2014. The two nations are targeting to raise the trade to USD 30 billion in the next five years.
(With inputs from PTI)