US Homeland Security Secretary Michael Chertoff is downplaying concerns that al-Qaida-inspired elements might use weapons of mass destruction to attack the West. Chertoff told students and journalists gathered Friday at the Oxford Union debating society in England that the United States is more concerned that terrorists will use conventional weapons against America. He said it was less likely that nuclear or biological weapons would be used. His remarks followed the release of a video which exhorts jihadis to use nuclear or biological weapons against the United States. The video began appearing on al-Qaida-affiliated internet forums in late April and presents the US as vulnerable to such attacks.