UNITED NATIONS - Secretary-General Ban Ki-moon urged world leaders on Tuesday to stop fueling the bloodshed in Syria with weapons and get both sides to the negotiating table to end the "biggest challenge to peace and security in the world."
In his state of the world address to open the annual gathering of presidents, prime ministers and monarchs at the U.N. General Assembly, the U.N. chief said the international response to last month's "heinous use of chemical weapons" in Syria "has created diplomatic momentum - the first signs of unity in far too long."
He called on the U.N. Security Council to adopt an "enforceable" resolution on a U.S.-Russian agreement to put Syria's chemical weapons under international control for destruction and bring to justice the perpetrators of the Aug. 21 chemical weapons attack outside Damascus "either through referral to the International Criminal Court or by other means consistent with international law."
U.N. diplomats say differences between the U.S. and Russia on how a resolution should be enforced have held up action in the Security Council. Russia is opposed to any mention of Chapter 7 of the U.N. Charter, which includes military and non-military actions to promote peace and security. Russia and China have vetoed three Western-backed resolutions that would have pressured Syrian President Bashar Assad to end the 2 1/2-year war that has killed more than 100,000 people.
U.S. President Barack Obama echoed Ban, saying there must be "consequences" in a Security Council resolution to verify that Assad's regime is keeping his commitments.
"If we cannot agree even on this, then it will show that the U.N. is incapable of enforcing the most basic of international laws," Obama said.
Obama also addressed the other issue expected to dominate this year's ministerial session which ends Oct. 1 - the first appearance on the world stage of Iran's new president, Hasan Rouhani. No U.S. president has met with an Iranian leader since the 1979 Islamic revolution, but U.S. secretaries of state and Iranian foreign ministers have had occasional encounters, the most recent in 2007.
Obama welcomed Iran's "more moderate course" under Rouhani, saying it offers the basis for a breakthrough in negotiations with six key nations on its disputed nuclear program. He said he was charging Secretary of State John Kerry to pursue progress on the nuclear issue, saying the "diplomatic path must be tested."
Foreign ministers of the six countries - the U.S., Russia, China, Britain, France and Germany - are scheduled to meet Thursday with Iran's Foreign Minister Mohammad Javad Zarif, who sat behind Iran's sign in the General Assembly listening intently to Obama's speech.
Obama also addressed Iranian and Russian support for the Syrian regime.
"It's time for Russia and Iran to realize that insisting on Assad's rule will lead directly to the outcome they fear: an increasingly violent space for extremists to operate," Obama said. "In turn, those of us who continue to support the moderate opposition must persuade them that the Syrian people cannot afford a collapse of state institutions, and that a political settlement cannot be reached without addressing the legitimate fears of Alawites and other minorities."
Turkish President Abdullah Gul welcomed the U.S.-Russian agreement to destroy Syria's chemical weapons but said that should not allow those who perpetrated a "crime against humanity" by using the weapons against civilians to escape justice.
Gul, whose nation borders Syria to the north and hosts refugees from the conflict, also lamented that "geopolitical considerations" had stymied Security Council action to stop the fighting.
"It is a disgrace that the United Nations Security Council has failed to uphold its primary responsibility in this case," he said, predicting that if the international community fails to act, the death toll would double by next year.
Ban stressed that the international community "can hardly be satisfied with destroying chemical weapons while the wider war is still destroying Syria," and he stressed that the "vast majority" of the killing has been carried out with conventional weapons
"I appeal to all states to stop fueling the bloodshed and to end the arms flows to all parties," the secretary-general said.
Ban decried the plight of the more than 7 million Syrians forced to flee their homes and called on the Syrian government and opposition to "lift all obstacles" to access for humanitarian workers and release "the thousands of men, women and children whose detention has no basis in international law."
Beyond Syria, the secretary-general said, "we can see tremendous stress and upheaval across the region."
"Historic transitions have stumbled or slowed. Springs of inspiration are giving way to winters of disillusionment," Ban said, without naming any countries. "The challenges are immense: building democracy and pluralistic dialogue; dousing the flames of sectarianism; filling the security vacuum after the iron grip of dictators is gone."
The secretary-general also welcomed the revival of direct negotiations between Israel and the Palestinians. And he declared, "Let the 21st century be the century of women."
Ban announced that the U.N. will hold a climate summit next September in New York and challenged leaders to bring "bold pledges" to close the emissions gap.
On another issue that has had worldwide repercussions, Brazil's President Dilma Rousseff lashed out at the United States for its electronic spying program.
Brazil is an important hub for trans-Atlantic fiber optic cables, and the National Security Agency has reportedly intercepted her communications with aides, hacked into the computer network of a state-run oil company and scooped up data from billions of emails and telephone calls flowing through the country.
Rousseff last week shelved an upcoming state trip to Washington in a show of anger over the NSA surveillance program.
"Tampering in such a manner in the affairs of other countries is a breach of international law and is an affront to the principles that must guide the relations among them, especially among friendly nations," she said. "A sovereign nation can never establish itself to the detriment of another sovereign nation."
Associated Press Writers Matthew Pennington and Lara Jakes at the United Nations contributed to this report.