U.N. Summit Leaders Say Assad Must Go

U.N. chief Ban Ki-moon on Tuesday said the Syria "calamity" is turning into a global crisis as U.S. President Barack Obama led growing calls for an end to Bashar Assad's rule.

Condemnations of Assad marked the opening day of the U.N. General Assembly of world leaders, as the conflict passes 18 months and the international community remains deadlocked over how to end the bloodshed.

The conflict "is a regional calamity with global ramifications" that needs action by the Security Council, Ban said in the opening address of the assembly.

"The international community should not look the other way as violence spirals out of control," Ban told world leaders, adding that "brutal" rights abuses were being committed by Assad's forces.

He said the Security Council and countries in the region must "solidly and concretely" support peace efforts by U.N.-Arab League envoy Lakhdar Brahimi.

"We must stop the violence and flow of arms to both sides and set in motion a Syrian-led transition as soon as possible," Ban added.

The 15-nation Security Council has become paralyzed by deadlock over the conflict which Syrian activists say has left more than 29,000 dead.

Russia, Assad's main ally, and China have vetoed three Security Council resolutions which could have led to sanctions against the Syrian government.

Obama said there had to be "sanctions and consequences" for atrocities committed in the war and that Assad must go. He also said that Iran "props up a dictator in Damascus."

"The future must not belong to a dictator who massacres his people," Obama told the assembly.

"If there is a cause that cries out for protest in the world today, it is a regime that tortures children and shoots rockets at apartment buildings."

He told leaders: "As we meet here, we again declare that the regime of Bashar Assad must come to an end so that the suffering of the Syrian people can stop, and a new dawn can begin."

Obama also warned that the international community must stop the uprising against Assad turning into "a cycle of sectarian violence."

He said the United States wants a Syria "that is united and inclusive; where children don't need to fear their own government, and all Syrians have a say in how they are governed -- Sunnis and Alawites; Kurds and Christians."

"That is the outcome that we will work for -- with sanctions and consequences for those who persecute; and assistance and support for those who work for this common good," Obama said.

"We believe that the Syrians who embrace this vision will have the strength and legitimacy to lead."

Brazil's President Dilma Rousseff, whose country hesitated over action against Assad when it was on the U.N. Security Council, said that the government "bears the largest share of responsibility" for the violence.

But she also highlighted the role of opposition groups "especially those that increasingly rely on foreign military and logistical support."