Modi will be undertaking a seven-day trip to Ireland and the US from September 23.
In the first leg of the two-nation tour, he will visit Ireland, marking first Prime Ministerial visit from India in almost 60 years, he said in a statement.
"In Ireland I 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," Modi said, adding he will also interact with the Indian community.
"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," the Prime Minister said.
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"I am sure my US visit will be fruitful and further deepen the bond between the world's oldest and largest democracies," he said.
Modi said he was going to USA at a "historic moment" when the United Nations 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 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," the Prime Minister said.
"I will also participate in a summit hosted by President Obama on peacekeeping," he added.
He 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.