US President Barack Obama will be the chief guest at India's Republic Day parade in January, the two countries announced Friday.
Obama will be the first United States president to be the guest of honour on the occasion, in a move that signals India-US ties are moving in the right direction following Modi's visit to Washington last month.
Modi broke the news first in a tweet, "This Republic Day, we hope to have a friend over… invited President Obama to be the 1st US president to grace the occasion as chief guest."
The White House responded with a statement, and a series of tweets, to confirm.
"At the invitation of Prime Minister Modi, the President will travel to India in January 2015 to participate in the Indian Republic Day celebration in New Delhi as the Chief Guest," a statement by the White House press secretary said.
"This visit will mark the first time a US president will have the honor of attending Republic Day, which commemorates the adoption of India's constitution. The President will meet with the Prime Minister and Indian officials to strengthen and expand the U.S.-India strategic partnership."
US official and congressional sources said this was a "major gesture" from Obama as he has agreed to be out of the country around the time of the annual State of the Union address, at which the president presents his annual report at a joint session of Congress.
Also, "owing to their busy schedule, US presidents don't usually go for ceremonial functions," said Lalit Mansingh, former foreign secretary and Indian ambassador to the US.
This will be Obama's second visit to India, also a record of sorts as no US president has been to India twice while in office. His first was in November 2010, during the United Progressive Alliance (UPA) government's tenure, at the invitation of then prime minister Manmohan Singh. He had addressed a joint session of parliament.
Modi had invited Obama to visit India during their meetings at the White House in October, but it was open ended and without specifics. The president had accepted, according to a joint statement.
On his return, Modi extended the Republic Day invitation to Obama during one of their conversations, said ministry of external affairs spokesperson Syed Akbaruddin. A formal letter followed, and Obama accepted.
Modi's tweet, however, was the first public announcement. That was new, and newer still was how news about it broke.
"By tweeting India's R-Day invite to Obama, PM Modi is rewriting the rules of diplomatic protocol. Bravo! Breath of fresh air in diplomacy," tweeted Sanjaya Baru, ex-media adviser to former PM Manmohan Singh.
During his recent five-day hectic visit to the US, Modi had projected India as an attractive investment destination, tried to reset ties with America, addressed the UN General Assembly and enthralled the Indian diaspora.
Modi and Obama had hit it off immediately at their first meetings, according to accompanying US and Indian officials. And there were two - first was an informal dinner.
The next morning, the president personally gave the PM a tour of the Martin Luther King memorial, signalling a closeness that was hard to miss.
Before leaving, Modi "thanked" America for what he said was a highly "successful and satisfactory trip" to the country.
The two leaders said they covered key issues including economics, climate change and regional security besides agreeing to negotiate a 10-year extension of a military cooperation framework due to expire at yearend, and joint efforts against terrorism and militant networks such as Lashkar-e-Taiba.
Modi and Obama met for the second time in six weeks at the ASEAN Summit in Myanmar this month.
Thaw in ties
Modi, as the Gujarat chief minister was denied by the US an official visa in 2005, and was deprived of his tourist-business visa in the aftermath of the 2002 riots.
But, the US signalled a thaw in ties in the run-up to the 2014 Lok Sabha elections, in which Modi's Bharatiya Janata Party (BJP) secured a landslide victory.
President Obama did call to congratulate Modi - though he was not the first, other world leaders beat him to it - and invited him to the White House.