Ahead of the visit, Mr Modi said he was going to USA at a "historic moment" when the UN is celebrating its 70th anniversary.
Prime Minister Narendra Modi will embark, today, on a two-nation tour of Ireland and USA amid his confidence that his visit will help further deepen ties with these two countries.
In the first leg of his seven-day trip, he will visit Ireland, marking first Prime Ministerial visit from India in almost 60 years.
In Dublin, he will hold talks with Enda Kenny, the Taoiseach of Ireland.
"We hope to further develop strong people-to-people and economic ties with Ireland in the years to come," Mr Modi said ahead of the visit.
He will also have a brief interaction with the Indian community before leaving for New York in the evening.
In New York, Mr Modi will address a UN Sustainable Development Summit and participate in a Summit on peacekeeping being hosted by US President Barack Obama.
The Prime Minister will also be meeting several world leaders and have interactions with leading investors and financial sector firms. There will be a working dinner where major Fortune-500 companies will be present to deliberate on investment opportunities in India.
He will also travel to West Coast where he will visit Facebook Headquarters for a Townhall Q&A with its CEO Mark Zuckerberg. He will also visit Google campus and Tesla Motors.
In San Jose, he will interact with the Indian community on September 27.
"This visit seeks to build on the substantial ground covered during my last visit to USA and President Obama's visit to India early this year," he had said.
"I am sure my US visit will be fruitful and further deepen the bond between the world's oldest and largest democracies," he said.
Ahead of the visit, Mr Modi said he was going to USA at a "historic moment" when the UN is celebrating its 70th anniversary.
"India attaches great importance to the United Nations.
In July, I had written a letter to heads of governments of 193 nations outlining India's vision for UN agenda and reforms. I am glad that leaders of several nations wrote back appreciating our vision," he had said.
In the context of the UN Sustainable Development Summit for formal adoption of post-2015 new sustainable development agenda, he said, "Coming from a culture that regards harmony as central to its ethos, I am glad to have an opportunity to address this forum. The new goals are closely aligned with India's vision for sustainable development and our flagship programs for the same."
With regard to the Summit on peacekeeping, the Prime Minister noted that India has historically been one of the largest contributors to the UN peacekeeping forces with 1,80,000 Indian troops having participated in UN peacekeeping missions - more than from any other country.
"We are proud of our peacekeeping forces spread across the world, ensuring peace in difficult circumstances. I will pay homage to all those brave men and women who sacrificed their lives for peace. And I look forward to sharing my thoughts on how to make peacekeeping more effective," he said.
This year, India will host a summit of G-4 leaders in New York where the main agenda would be the UNSC reforms.
"The 70th anniversary of the UN is an apposite moment for reform discussions to be accelerated. Recently, the UN General Assembly finally adopted a document after over 20 years that would form the basis of formal discussions on this matter," the Prime Minister said.
Referring to his visit to West Coast, he said he was enthusiastic about the 'India-US Start-up Konnect' event where a group of Indian start-ups will showcase their innovations and forge partnerships with the vibrant American start-up industry.
In San Jose, he will interact with the Indian community on September 27.
"The Indian diaspora has left no stone unturned in strengthening India-USA ties. We are very proud of the accomplishments of our diaspora that has made immense contributions to both our societies," he said.