France gave its backing to the US plans after British lawmakers voted against any involvement in military action against Damascus and other close allies including Germany said they would not sign up.
The White House has signalled that Obama, guided by the "best interests" of the United States, was ready to go it alone on Syria after accusing President Bashar al-Assad's regime of using chemical weapons against its own people.
In Damascus, UN experts carried out their final investigations into the attacks east of the capital that activists say killed more than 300 people, visiting a hospital where victims were reportedly being treated.
The team is due to leave the war-battered country tomorrow and report back immediately to UN chief Ban Ki-moon, who has appealed to the West to allow time for their findings to be assessed.
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Ban is due to meet ambassadors from the five UN Security Council permanent members at 1600 GMT, while US Secretary of State John Kerry will make a statement on the Syria crisis at 1630 GMT.
While Germany and Canada ruled out joining any military strikes, French President Francois Hollande -- whose country was a strident opponent of the US-led war on Iraq -- said the British decision would not affect his government's stance.
"France wants firm and proportionate action against the Damascus regime," Hollande said in an interview with Le Monde newspaper.
US Defence Secretary Chuck Hagel said the White House was still seeking an "international coalition that will act together" against Assad's regime.