Washington:
President Barack Obama will seek to leverage his burgeoning bond with Indian Prime Minister Narendra Modi into progress on climate change, defense and economic ties as he opens a three-day visit to New Delhi.
Relations between the US and India have been strained in recent years, but President Obama and PM Modi developed a good rapport during a visit in Washington last fall. PM Modi sought to return the favor by inviting Mr Obama to travel to India as his guest for the annual Republic Day festivities, which mark the day in 1950 that the country's constitution came into force.
"It took us by some surprise," said Ben Rhodes, Obama's deputy national security adviser. "There's a great affinity between the United States and India and our people, but there's also a history that is complicated and that would have made it seem highly unlikely that a US president would be sitting with India's leaders at their Republic Day ceremony."
After some internal deliberations, the White House accepted PM Modi's offer. The visit also includes a fresh round of bilateral meetings with PM Modi, an economic summit with US and Indian business leaders.
Obama will be the first US president to visit India twice while in office; he also traveled there in 2010 for an economic summit. First lady Michelle Obama will be with the President when he arrives in New Delhi on Sunday.
The President's visit is expected to be heavy on symbolism and lighter on substantive advances, though climate change, economics and defense ties are all on the agenda. Indian political commentator Ashok Malik said expectations for concrete deliverables during the visit are "below the standards usually set by US presidents when they travel across the world for a three-day visit."
Still, US and Indian officials appear to agree that even a symbolic show of solidarity between the leaders would be a sign of progress after recent difficulties.
While military cooperation and US defence sales have grown, Washington has been frustrated by India's failure to open up to more foreign investment and to address complaints alleging intellectual property violations. India's liability legislation has also prevented US companies from capitalising on a landmark civil nuclear agreement between the two countries in 2008.
Relations hit a new low in 2013 when India's deputy consul general, Devyani Khobragade, was arrested and strip-searched in New York over allegations that she lied on visa forms to bring her maid to the US while paying the woman a pittance. The official's treatment caused outrage in New Delhi, and India retaliated against US diplomats.
For PM Modi, hosting President Obama at the Republic Day parade caps off a year of high-profile diplomatic maneuvers by a leader who was once shunned by the international community. He was denied a US visa in 2005, three years after religious riots killed more than 1,000 Muslims in Gujarat where he was the top elected official.
The visit ties in neatly with PM Modi's election promise that he would turn around Asia's third-largest economy. And it could send a message to Pakistan and China - India's closest neighbors and rivals - that PM Modi has a powerful ally in the United States.
"PM Modi has used the invitation as a way of signaling that the United States really looms large in his calculations for where he want to take India," said Ashley Tellis, a senior associate at the Washington-based Carnegie Endowment for International Peace.
US officials say they hope the improving relationship between President Obama and PM Modi will have payoffs in the policy arena. The White House plans to push India on climate change, particularly after reaching a sweeping agreement with China on limiting carbon emissions. The President will also be accompanied on his trip by several US business leaders in hopes of forging new partnerships with India.
The centerpiece of Mr Obama's visit will be Monday's celebrations, which are partly a Soviet-style display of India's military hardware and partly a Macy's Thanksgiving Day-type parade with floats from across the country highlighting India's cultural diversity.
The parade, once a huge attraction, has lost much of its sheen for India's elite over the past decade. But it continues to draw tens of thousands of visitors eager to view the spectacle at least once in their lifetimes.