A witness to the US raid in Syria has described how dozens of commandos arrived in the middle of the night on heavily armed helicopters.
Syria has started moving chemical weapons materials out of the country as part of the disarmament programme, which has faced technical problems.
Britain will not join any military action against Syria after a stunning parliamentary defeat of a government motion on the issue.
Syria warned the US against action over a suspected poison gas attack, saying it would "create a ball of fire that will inflame the Middle East".
The Pentagon said US F-16s would to stay in Jordan, as Russia bristled at the possibility they could be used to enforce a no-fly zone inside Syria.
Syria and Iran joined forces on Saturday to condemn moves by Western powers to aid rebels fighting against President Bashar al-Assad.
A fourth member of Syrian President Bashar al-Assad’s inner circle has died from a bomb attack this week as rebels converge on the capital.
Syrian rebels have killed at least 25 members of militia loyal to President Bashar al-Assad and troops killed 10 protesters in Aleppo.
Nine people are dead and 100 wounded in bomb blasts near Syrian security service buildings as a bombing battle intensifies against government targets.
Activists accuse Syrian troops of shelling two cities in an effort to weaken forces fighting Bashar al-Assad’s government before a ceasefire deadline.