UN Secretary-General Ban Ki-moon warned world powers Thursday not to repeat in Syria the mistakes they made in Bosnia, during a landmark visit to Srebrenica where UN peacekeepers failed to prevent the massacre of 8,000 Muslim men and boys.

Ban said after laying flowers at a white marble memorial to the Srebrenica victims, “I don’t want to see any of my successors after 20 years visiting Syria and apologizing for what we could have done now to protect civilians in Syria, which we are not doing.”

“Never Srebrenica,” he said, “Nowhere, to nobody.”

Meanwhile, Saudi Arabia’s UN Ambassador Abdallah Al-Mouallimi said that the Kingdom is proposing a General Assembly resolution which will highlight a Syrian government threat to use chemical weapons.

The new Arab initiative follows the failure of a western-attempt to get the UN Security Council to threaten sanctions against Syria’s President Bashar Al-Assad over the 16-month-old conflict, diplomats said.

Al-Mouallimi told a group of reporters the resolution would be submitted in coming days and he hoped for a vote “probably early next week.”

Asked whether the resolution would mention the Syrian government’s threat made this week to use its chemical weapons if attacked, Al-Mouallimi said that “it will reference all of the issues that are of significance in the Syrian situation.”

UN diplomats said the resolution could call on the 193 UN member states to follow sanctions that have been ordered against Syria by the Arab League.

That would be opposed by Russia and China after their veto last Thursday.

The resolution could also demand humanitarian access to conflict-stricken parts of Syria, the diplomats said on condition of anonymity as talks on the resolution are still private.

The UN General Assembly cannot force legally binding sanctions, like the 15-nation Security Council. But no country can veto any of its resolutions which just need a majority.

A General Assembly resolution passed in February brought the Syria conflict back to the forefront of UN debate after Russia and China blocked two earlier Security Council resolutions. “The Arab states are frustrated at the lack of international action on Syria, particularly the vetoes by Russia and China,” said one UN diplomat.

Meanwhile, Syrian troops prepared to launch an all-out offensive on rebel-held districts across Aleppo, a security source said, as pro-regime media warned of a looming “mother of all battles.”

Fighting raged in parts of Syria’s most populous city through the night and into Thursday, but the security source said the main offensive was still to come.