Any faction found to have used chemical weapons "must be brought to justice,"
Ban appealed for patience among U.N. member states while an investigative team that returned from Syria over the weekend completes analysis of biomedical and environmental samples it collected.
The team, which spent four days in search of evidence that chemical attacks occurred Aug. 21, will have delivered all of its forensic evidence to European labs for analysis by Wednesday, Ban said at U.N. headquarters in New York at a webcast news conference.
"We need to emphasize the importance of not jeopardizing the scientific timelines needed for accurate analysis," he said, without providing any specifics on when the results will be available and made public.
The U.N. investigators, led by Swedish scientist Ake Sellstrom, were tasked solely with determining whether chemical weapons were used, not who used them, in attacks in Damascus suburbs that U.S. intelligence reports say killed more than 1,400 people.
Asked whether threatened
"The use of force is lawful only when in exercise of self-defense in accordance with Article 51 of the United Nations Charter and-or when the Security Council approves such action," Ban said.
"I take note of the argument for action to prevent a future use of chemical weapons," the U.N. chief added. "At the same time, we must consider the impact of any punitive measure on efforts to prevent further bloodshed and facilitate the political resolution of the conflict."
Ban appealed for Security Council member states to "come together on an appropriate response" to the chemical weapons issue. He also urged "regional and international actors to convene the Geneva conference as soon as possible."
U.S. Secretary of State
Numerous attempts to get a Security Council resolution to sanction or condemn Assad's conduct of the war have failed because of opposition by Russia and China. Russia is Syria's most powerful ally and primary arms supplier, and China resists on principle any effort to exert outside pressure on a state's internal affairs.
Last week, U.S.-led airstrikes backed by allies including France and Australia appeared imminent as pressure mounted to punish Assad for violating the global ban on the use of chemical, biological and nuclear weapons. But President