Ban spoke in Tehran at the Non-Aligned Movement meeting. He said the United Nations plays a crucial role in responding to the early stages of conflict.
"The crisis in Syria started with peaceful demonstrations that were met by ruthless force," said Ban. "Now, we face the grim risk of long-term civil war destroying Syria's rich tapestry of communities."
Members of the U.N. Security Council, however, have been unable to pass a resolution condemning the Syrian government for its assault on civilians.
Veto-wielding members China and Russia say resolutions drafted so far lack balance. Russia is one of Syria's top weapons suppliers.
Ban said those who provide weapons to either side of the conflict are contributing to the country's misery.
"There should be no more bullets and bombs," he said.
Human Rights Watch has called on Syria's neighbors to keep borders open for refugees fleeing the violence in Syria. An estimated 200,000 refugees have sought refuge in Turkey, Iraq, Jordan and Lebanon, the organization said.
The rights group reminded Israel that forced returns of Syrians was unlawful.