The United States tripled Wednesday the number of helicopters helping Pakistans flood relief effort, as top US officials issued somber warnings about the massive scale of the disaster. The boost in the US deployment came as outgoing UN humanitarian chief John Holmes appealed for $460 million in emergency aid for up to 14 million people reeling from Pakistans worst floods in living memory. US Defense Secretary Robert Gates said the USS Peleliu, an amphibious assault ship, was moored off Karachi awaiting the green light to dispatch its 19 helicopters to the disaster zone. The flooding in Pakistan has the potential to be significantly more disastrous for the country than the earthquake several years ago, Gates said, referring to the 2005 Kashmir earthquake that killed more than 73,000 people. The (US) president (Barack Obama) wants to lean forward in offering help to the Pakistanis, Gates said. We will work with them (the Pakistanis) and do this at their pace.