(AP) - Vladimir Putin played it cool, Barack Obama was earnest but firm and Iran's president walked in smiling. World leaders glided through the opening day of a U.N. gathering Monday that aims to wrestle with the globe's biggest crises - a historic flood of refugees, the rise of threats like the Islamic State group and the conflict in Syria.

The U.N. secretary-general for the first time called for the civil war in Syria to be referred to the International Criminal Court, while Iranian President Hassan Rouhani said Iran's recent nuclear deal with world powers had a broader goal: "We want to suggest a new and constructive way to recreate the international order."

Chinese President Xi Jinping made a $1 billion pledge for U.N. peace efforts.

And 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."

"When and how did fear and intimidation creep so insidiously into our conversation when there is so much more to be said about the love of God?" he asked, also quoting the Quran on mercy.

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 percent of Jordan's population. Iraq and Turkey also groan under the strain of millions of refugees.

In his state of the world address to leaders from the U.N.'s 193 member states, Ban Ki-Moon called for a political solution to the conflict in Syria, now well into its fifth year with more than a quarter of a million people killed.

Ban said five countries "hold the key" to a political solution to Syria: Russia, the U.S., Saudi Arabia, Turkey and Iran.

Obama and 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 U.S. is prepared to work with any country, including Russia and Iran, to resolve Syria's conflict, Obama said.

The U.S. president also took jabs at Russia and China, without naming names. "The strong men of today become the spark of revolution tomorrow," Obama warned. And he added in a critique of restrictions on speech, "You can control access to information ... but you cannot turn a lie into truth."

Putin, who showed up at the U.N. gathering for the first time in a decade and was not at Russia's seat in the chamber when Obama spoke, 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 and called it "an enormous mistake to refuse to cooperate" with the Syrian government.

Ukraine's table just in front of the speaker's stand was empty as Putin spoke. The country struggles against pro-Russia separatists in its east, while Russia denies supporting them.

Rouhani appeared to align with Putin's call for a U.N. Security Council resolution consolidating the fight against terror, saying "we propose that the fight against terrorism be incorporated into a binding international document and no country be allowed to use terrorism for the purpose of intervention in the affairs of other countries."

Meanwhile, Obama announced that more than 30,000 new troops and police have been pledged to U.N. peacekeeping missions from more than 50 countries. He spoke at a high-level meeting chaired by the U.S. to strengthen and modernize peacekeeping, which increasingly faces threats from extremist groups while being severely stretched in personnel and equipment.

Other issues at the center of this week's discussions include the refugee and migrant crisis, the largest since the upheaval of World War II.

Ban warned that resources to address them are dangerously low. "The global humanitarian system is not broken; it is broke," he said. The U.N. has just half of what it needs to help people in Iraq, South Sudan and Yemen, and just a third of what's needed for Syria.

The U.N. chief, in unusually hard-hitting words, also blamed "proxy battles of others" for driving the fighting in Yemen, and he warned against "the dangerous drift" in resolving the Israeli-Palestinian conflict, saying it is essential for the international community to pressure both sides to re-engage.

Others speaking Monday included French President Francois Hollande, who again declared that Assad "cannot be part of the solution" to the Syrian conflict, and Cuban President Raul Castro, who also has a meeting planned with Obama.

Some, including Obama, Xi and Hollande, already addressed the General Assembly over the weekend during a separate global summit on sweeping new U.N. development goals for the next 15 years.