By Angus McDowall and Suleiman Al-Khalidi BEIRUT/AMMAN (Reuters) – The Syrian government stepped up its efforts on Thursday to retake the opposition’s last besieged enclaves, as rebels prepared to withdraw from one and a newspaper reported an ultimatum against another. President Bashar al-Assad scored a major victory this month by retaking eastern Ghouta, the biggest rebel stronghold near Damascus, putting his forces in by far their strongest position since the early months of the seven-year-old civil war. The United States, Britain and France launched a volley of air strikes on Saturday against three Syrian targets in retaliation for a suspected chemical weapons strike during the Ghouta assault.
