UNITED NATIONS: U.N. Secretary-General Ban Ki-moon said on Tuesday the "door may be closing, for good" on a two-state solution to the Israeli-Palestinian conflict, saying the continued growth of Jewish settlements undercuts peace.

"The two-state solution is the only sustainable option. Yet the door may be closing, for good," Ban told the U.N. General Assembly. "The continued growth of Israeli settlements in the occupied Palestinian territory seriously undermines efforts towards peace. We must break this dangerous impasse."

In an apparent reference to recent comments by Israeli, Iranian and U.S. officials, Ban also told the 193-nation assembly at the opening of its annual gathering of world leaders that he rejected threats of military action by one state against another.

While he did not specify which countries he was talking about, after criticizing Israeli settlement building, Ban told the assembly: "I also reject both the language of delegitimization and threats of potential military action by one state against another. Any such attacks would be devastating."

On the question of Syria's 18-month conflict, Ban said the world must "stop the violence and flows of arms to both sides, and set in motion a Syrian-led transition as soon as possible."

"The international community should not look the other way as violence spirals out of control," he said. "Brutal human rights abuses continue to be committed, mainly by the government, but also by opposition."

Brazilian President Dilma Rousseff and U.S. President Barack Obama are also due to address the assembly on Tuesday morning.