"I think there is no other country in the world today with which the United States shares so many common vital interests,' Blackwill said.
The former ambassador to India, who was also a former deputy assistant to President George W Bush, said these common vital interests embrace five areas, including fighting terrorism, concerns about weapons of mass destruction and rise of Chinese power.
"There may be ups and downs in our relationship, but over time these vital national interests that the two countries share will bring them together," Blackwill said while delivering the keynote at the Third annual India Investment Forum.
Blackwill noted that India was the only democracy in the 50 years after the Second World War with which the United States did not have good relations for a variety of reasons, most of them related to Cold War. He said up till 1990 it was an extremely difficult relationship, which was paradoxical in the sense that the relationship between the people of the two countries had always been strong.
"But things have changed. In fact, no other bilateral relationship has been so fundamentally altered as the US-India relationship," Blackwill said.
The ambassador said that the US-India civilian nuclear energy cooperation is in the last stage in the Congress. "It has passed the House and it may pass the Senate this week itself. This will normalise India's civilian nuclear relationship with the world led by the United States," Blackwill said.
"It looks like it will be signed onto a law by the President which is going to be a very big step forward in our relationship," he said.
Addressing potential investors and CEOs of American companies looking for investments in India or doing business with the country, he said that Indians are 'not like westerners'. They are the beneficiaries of a 5,000-year-old civilisation.
"I urge American CEOs and potential investors (to remember) that this is a country where relationships matter and you cannot fly there on Tuesday and fly out on Thursday, which, sadly, so many American executives were tempted to do, at least then, and succeed,' Blackwill said.
He said India is a country, which has every reason to feel confident about itself and it has a future in every respect and in every field.
"Although we have differences with India, these will be manageable in the long term. This is a country which has an extremely bright future,' Blackwill said.