The foreign ministers also said those responsible for the
attack should face trial, as other "war criminals" have
done.
Earlier, Saudi Arabia and the Syrian opposition pleaded
with League members to back a US military strike on the
regime.
Saudi Foreign Minister Saud al-Faisal told the meeting
that "opposition to international action only encourages the
regime to pursue its crimes".
"It is time to ask the international community to assume
its responsibilities and to take deterrent measures" against
the Syrian regime," al-Faisal said.
The head of the Syrian National Coalition, Ahmed
al-Jarba, told the meeting that the "war machine" of Assad
must be stopped.
"I am here before you today to appeal to your brotherly
and humanitarian sentiments and ask you to back the
international operation against the destructive war
machine," he said.
The umbrella coalition of opposition groups has been
recognised by the League as Syria's representative following
the barring of Assad's regime in 2011.
However, some influential members of the League,
including Egypt, Iraq, Lebanon, Tunisia and Algeria, have
expressed opposition to foreign military intervention.
Egypt's foreign minister on Sunday said that his nation
objected to "any aggression in Syria".
The US says it has evidence that the Assad regime
launched the August 21 chemical attack on the outskirts of
Damascus, which it says killed more than 1,400 people. Other
estimates by aid groups are more conservative, putting the
toll in the hundreds.
The Syria regime denies it was behind the attacks. The
Arab League last week condemned the attack, but said any
action must be mandated by the United Nations.