US President Barack Obama has declared one of the largest relief efforts in US history to help Haiti's earthquake victims as survivors begged for aid still only trickling through to them. Four days after a massive quake, hundreds of thousands of Haitians are still desperately waiting for assistance as scavengers and looters preyed on shattered buildings in the widespread absence of authority and order. Even as aid poured into Port-au-Prince airport, thousands of Haitians streamed out on foot with suitcases on their heads to find food, water and shelter in the countryside and flee aftershocks as well as violence.<br/><br/>Obama promised help as US Secretary of State Hillary Clinton flew to Haiti where the shell-shocked government gave the United States control over its main airport to guide aid flights from around the world.<br/><br/>With the government saying up to 200,000 people may have been killed, the quake could be one of the ten deadliest in history.<br/><br/> <br/>