The UN secretary-general for the first time called for the Syrian crisis to be referred to the International Criminal Court, while Chinese President Xi Jinping boosted support for international peacekeeping.
Jordan's King Abdullah II made a heartfelt defense of the kinder side of the Muslim world in the face of "the outlaws of Islam that operate globally today."
The king has called the rise of extremist groups like the Islamic State, and the crises they have caused, "a third world war, and I believe we must respond with equal intensity."
Jordan borders both Syria and Iraq, and Syrian refugees now make up 20 per cent of Jordan's population. Iraq and Turkey also groan under the strain of millions of refugees.
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Ban Ki-moon's state of the world address to leaders from the UN's 193 member states insisted on a political solution to the conflict in Syria, now well into its fifth year with more than a quarter of a million people killed.
President Barack Obama and Russian President Vladimir Putin, hours ahead of their first face-to-face meeting in nearly a year, gave no sign of closing their deep divide on the Syrian crisis.
Obama said of Syrian President Bashar Assad, "when a dictator slaughters tens of thousands of his own people, that is not a matter of a nation's internal affairs."
The US is prepared to work with any country, including Russia and Iran, to resolve Syria's conflict, Obama said.
The US president also took jabs at Russia and China, without naming names.
Putin, who showed up the UN gathering for the first time in a decade, called for the creation of a broad international coalition against terror, following his country's surprising moves in recent weeks to increase its military presence in Syria and to share intelligence on the Islamic State group with Iran, Iraq and Syria.
The Russian leader dismissed the West's concerns about his country's ambitions in Syria, "as if they have no ambitions at all," and he called it "an enormous mistake to refuse to cooperate" with the Syrian government.