"Narenda Modi is an able man; we'll have to see how he conducts himself if he rises to the top," Frank Wisner, who had also served as Under Secretary of State for International Security Affairs, said in a teleconference organised by the Asia Society Policy Institute on US-India relationship.
"But doing business with him will be an imperative, assuming of course his party is able to form India's next government," he said.
We'll have to see how Modi conducts himself if he rises to the top: Ex-US envoy
"I think US businesses and key Indian constituents have accepted that they will have to do business with him. The relationship with India is too important to be held up on the issue of one man," Wisner said.
In 2005, the State Department had revoked a visa that Modi had for traveling to the US in the wake of the 2002 riots in Gujarat.
The US has repeatedly said there is no change in its long-standing visa policy relating to Modi but he is free to apply for a visa and await a review "like any other applicant."
On how the upcoming crucial general elections in India will play out, Wisner said while it is too early to predict the electoral outcome, it is "absolutely clear" that there will be major changes in the Indian political landscape.
He underscored that no matter what is promised during the election campaign, the next government in New Delhi must have one key priority of putting India back on a growth trajectory.