United Nations Secretary-General Ban Ki-moon accused the Syrian regime on Tuesday of killing the most civilians during the country's five year conflict and said "powerful patrons that keep feeding the war machine also have blood on their hands."

In his final address to the annual gathering of world leaders at the United Nations, Ban said the Syrian regime "continues to barrel bomb neighborhoods and systematically torture thousands of detainees."

"Present in this hall today are representatives of governments that have ignored, facilitated, funded, participated in or even planned and carried out atrocities inflicted by all sides of the Syria conflict against Syrian civilians," he said.

Ban said "many groups have killed innocent civilians — none more so than the government of Syria."

"I appeal to all those with influence to end the fighting and get talks started," Ban called on world leaders in his farewell address.

The prospects of a two-state solution in the Middle East "are being lowered by the day," Ban added, saying that the stalled peace process over his tenure as UN chief "has been 10 years lost to peace.""This is madness," Ban says. "Replacing a two-state solution with a one-state construct would spell doom: denying Palestinians their freedom and rightful future, and pushing Israel further from its vision of a Jewish democracy towards greater global isolation."

And he accused South Sudan's feuding leaders of betraying their people. He said "in too many places, we see leaders rewriting constitutions, manipulating elections and taking other desperate steps to cling to power."

Ban expressed regret for sexual abuse by U.N. peacekeepers and an outbreak of cholera in Haiti during his final address to the annual gathering of world leaders in New York.He said these two matters had "tarnished the reputation of the United Nations and, far worse, traumatized many people we serve." Ban will step down at the end of 2016 after serving two five-year terms.