The US troops were the most visible sign of a major international relief effort that had only just begun and could last for years, with aid agencies likening the scale of the destruction to the 2010 Haiti earthquake that killed tens of thousands.
"The level of destruction we're seeing reported is absolutely staggering," said Antonio Guterres, head of the UN refugee agency, which usually works only in conflict zones but which was organising an airlift due to the "exceptional nature" of the tragedy.
Many foreign governments have pledged help, with Australia donating nearly US$10 million.
Adding to concerns was a looming storm in the Pacific Ocean that threatened to dump heavy rain across Leyte and other devastated areas.
The depression is expected to hit land on the southern island of Mindanao late Tuesday, then move across the central islands of Bohol, Cebu, Negros and Panay, which all suffered typhoon damage, weather forecaster Connie Dadivas told AFP.