AMMAN – Syrian rebels and activists say they fear President Bashar Al-Assad's troops could resort to wider use of chemical weapons, unless the United States follows up on its pledge of military support with firm and swift action. After months of equivocating, President Barack Obama's administration said on Thursday it would arm rebels, having obtained proof the Syrian government used chemical weapons against fighters trying to overthrow President Bashar al-Assad. Western diplomats said the United States is considering imposing a no-fly zone in Syria, in what would be its first direct military intervention of the two-year-old civil war. Rebels inside Syria, frustrated by what they see as endless Western delays, said that public statements alone would not deter Assad and his pro-Iranian Hezbollah allies. They said Assad could shift the use of chemical weapons, so far reportedly deployed mainly to check rebel advances, to a more offensive capability for recapturing territory. “The U.S. announcement upped the ante but it remains a verbal response that will not change Assad's intentions,” said Abu Hamza Al-Dirani, a member of the Revolution Command Council in the southwestern Damascus suburb of Daraya, which activists said was hit by a sarin gas attack in April. “The regime remains undeterred. Assad regards everyone who is not supporting him a terrorist and he will not hesitate to commit another Halabja in Syria,” Dirani said. The Kurdish town Halabja in northern Iraq was target of a chemical weapons attack by Saddam Hussein's forces in 1988 that killed thousands of civilians. Washington said 100 to 150 people were killed in what it called “detected chemical attacks” in Syria. That is a tiny fraction of the 90,000 death toll from two years of conflict, yet it marks the crossing of a “red line” on the use of chemical weapons, US officials said. President Barack Obama's deputy national security adviser, Ben Rhodes, mentioned four cases since March – two around the northern city of Aleppo, one north of Homs and one east of Damascus — where chemical agents including sarin were used. — Reuters