British Prime Minister David Cameron\'s office said Wednesday that he and US President Barack Obama had no doubt Syrian President Bashar al-Assad\'s regime had used chemical weapons against its own people. \"Both leaders agreed that all the information available confirmed a chemical weapons attack had taken place, noting that even the Iranian President and Syrian regime had conceded this,\" a Downing Street spokesperson said after the two leaders spoke on the phone Tuesday night. \"They both agreed they were in no doubt that the Assad regime was responsible.\"