By Jonathan Marcus
BBC diplomatic correspondent, United Nations
President Obama's approach is in marked contrast to the Bush era
It was the first time that a US president had presided over a United Nations Security Council meeting at summit level.
That is an indication of the importance that President Barack Obama attaches to the issues of non-proliferation and disarmament.
In his Prague speech last April he set out his vision of a world free of nuclear weapons.
He accepted that this was an aspiration - it might well not be achieved in his life-time - but it is clear that he intends to move as far as possible down this track.
The unanimous backing for the US-drafted resolution - with all five of the declared nuclear weapons states on board (China, the US, Russia, Britain and France) - is a measure of the growing sense of urgency.
There is a growing fear amongst disarmament experts both inside and outside government that the whole machinery intended to prevent the spread of nuclear weapons - whose cornerstone is the Nuclear Non-Proliferation Treaty or NPT - is looking increasingly fragile.
The NPT agreement was essentially a bargain between the existing nuclear-armed powers and the non-nuclear countries.
The declared nuclear powers would move significantly towards disarmament and in the meantime would share the benefits of the peaceful uses of nuclear technology. Non-nuclear states would abandon any hopes of developing nuclear weapons.
But the bargain is looking increasingly thin.
North Korea pulled out of the NPT regime and is believed to have a small nuclear arsenal.
Efforts will continue to roll back nuclear programmes in North Korea and Iran
Iran is refusing to bow to UN Security Council pressure and halt its uranium enrichment programme amidst unresolved concerns that it too, might have ambitions to develop nuclear arms.
It denies this but so far has not gone far enough to allay international concerns.
North Korea and Iran have already stretched the fabric of the existing treaty.
If they continue on their course other countries in Asia and the Middle East might seek to develop nuclear arms themselves.
Furthermore as nuclear power spreads around the globe, there is a growing risk that nuclear know-how could encourage other countries to aspire to nuclear weapons.
Mr Obama's approach rests upon three main pillars.
First the nuclear-armed powers must demonstrate their own disarmament credentials in deeds rather than just words.
The US and Russia are pursuing a new strategic arms reduction treaty.
The Obama administration has signalled its desire to see the Test Ban Treaty ratified by the US Senate and enter into force.
Countries like nuclear Pakistan are outside the disarmament mainstream
And work is beginning on a new agreement to halt the manufacture of fissile materials for bomb-making.
Second the whole machinery of non-proliferation must be strengthened.
The Obama administration believes that there must be real consequences for those countries who abandon the treaty or who try to make fast and loose with its provisions.
The NPT agreement is up for revision in May and the new consensus at the UN Security Council sends a powerful signal that this key agreement must be bolstered.
Thirdly the nuclear bargain needs to be reinforced too.
Real efforts must be made to share and encourage the peaceful uses of nuclear energy.
It is a huge and complex agenda.
Separate efforts will continue to roll back North Korea and Iran's nuclear programmes.
The apparent shift in Russia's position on sanctions against Iran is seen as creating the best possible climate for talks that are due to begin with Iran at the start of October.
Another question, barely touched upon so far, is how to get countries like India, Pakistan and Israel - who are all thought to have nuclear weapons and who have never signed the NPT agreement - to become part of the disarmament mainstream.
Nonetheless after the Bush years, when the United States seemed sceptical at best about the merits of multilateral arms control agreements, Mr Obama is signalling that the US is back as a team player and that Washington now intends to lead by example.