In a unanimous decision, the United Nations Security Council approved a resolution Thursday to rid the world of nuclear weapons.

President Barack Obama presided over the rare summit in Pittsburgh, the first chaired by an American president.

Russia and China were among the 15-member council to support the measure, which steps up efforts to prevent the spread of nuclear weapons and promotes disarmament.

Obama called it a historic moment and says it shows a shared commitment to rid the world of nuclear weapons:

"Let me be clear. This is not about singling out individual nations, it is about standing up for the rights of all nations who do live up to their responsibilities," Obama said. "The world must stand together, we must demonstrate international law is not an empty promise, and the treaties must be enforced."

In his speech at the General Assembly Wednesday, the president said fixing the world's problems will require a global effort.

"Those who used to chastise America for acting alone in the world cannot now stand by and wait for America to solve the world's problems alone," he said. "We have sought, in word and deed, a new era of engagement with the world. Now is the time for all of us to take our share of responsibility for a global response to global challenges."

The rest of Wednesday's General Assembly session was marked by speeches from two controversial leaders.

While thousands protested outside, Iranian President Mahmoud Ahmadinejad lashed out at capitalism, and defended the legitimacy of his re-election. He said that Iran is ready to shake all hands that are honestly extended to his country.

And, in his first-ever speech to the UN, Libyan leader Moammar Gadhafi spoke for 98 minutes, going far over the 15 minutes allotted to him.

He touched on everything from the assassination of President John F. Kennedy to swine flu.

Gadhafi also said he would be happy if Barack Obama were president forever.

The speech went on so long that an exhausted interpreter needed to be relieved.

The U.S. delegation walked out before both Gadhafi and Ahmadinejad's speeches.