"America is pursuing a diplomatic resolution to the Iranian nuclear issue, as part of our commitment to stop the spread of nuclear weapons and pursue the peace and security of a world without them," he told the General Assembly.
"This can only happen if Iran takes this historic opportunity," Obama added.
"My message to Iran's leaders and people is simple: do not let this opportunity pass. We can reach a solution that meets your energy needs while assuring the world that your program is peaceful."
Talks between Iran and six powers, known as the P5+1 - Britain, China, France, Russia, the United States and Germany - are currently at a critical juncture.
The negotiations have only two months left to overcome hurdles in the way of a deal on curbing Tehran's nuclear program.