Syria says it will not use chemical weapons against its own people, but would do so against an external attack.
A foreign ministry spokesman said the weapons, stored and secured by the armed forces, would never be used inside Syria.
Earlier, the Arab League called on President Bashar al-Assad to step down, offering him safe passage.
Rebels say they are encouraged by the deaths of some high ranking officials last week.
Four officials, including the minister of defence and President Assad's brother-in-law, were killed in an attack in Damascus on 18 July.
