United Nations, Sep 24 - The United Nations Security Council in a rare meeting of heads of state, led for the first time by a US president, adopted a resolution Thursday focused on stopping the spread of nuclear weapons.

With President Obama acting as chairman, the council unanimously passed the resolution aimed at ensuring full compliance with international arms agreements from countries like North Korea and Iran, which have either banned inspectors or severely limited their access.

Obama said, though, that the resolution was not about singling out nations, but about ensuring that international agreements have real-world heft.

'International law is not an empty promise, and treaties must be enforced,' Obama said.

President Obama challenged the gathering to overcome cynicism against the goal of ridding the world of nuclear arms. He quoted president Reagan, saying 'a nuclear war can never be won and must never be fought.'

'The world must stand together,' Obama said. 'We must demonstrate that international law is not an empty promise.'

It was the first Security Council summit chaired by a US president, and only the fifth time that Security Council heads of state have met. Obama led the meeting because the United States holds the revolving presidency of the Security Council in September.