The message was clear. 'Killer Powell go home' read the huge banner draped over Athens most famous monument, the Parthenon, by anti-US demonstrators. And this morning US Secretary of State Colin Powell abruptly cancelled plans to attend tomorrow's Olympic Games closing ceremony. He cited work pressure, in particular the events in the Iraqi city of Najaf and the ongoing crisis in Sudan. In Washington the state department said anti-US demonstrations last night had played no plan in Powell's decision not to go to Greece. The protest movement has hailed the decision as a huge victory. A senior US official hinted his trip might have caused unspecified difficulties for Greece, which has mounted a hugely expensive security campaign to keep the Games safe. The demonstrations began last night. Around 1,500 anti-globalisation protesters and people who oppose American policies in the Middle East clashed with riot police. Officers used tear gas to stop the crowds making for the US Embassy. **PHOTO CAPTION*** Greek activists' banner on the Acropolis saying 'Powel killer go home' hours before a scheduled visit by the U.S. Secretary of State Colin Powell to Greece August 28, 2004. (REUTERS)