Mr Ban said he was "very upset" by the devastation he saw, adding that the international community stood ready to overcome the tragedy.
Western governments have backed Mr Ban's visit, calling for pressure on Burma's leadership to do more to help the cyclone victims.
UK Foreign Secretary David Milliband told the BBC: "The tragedy is that, for some people it is already too late, and it is certainly too little compared to the needs, but we have got to use the opportunity that exists.
"We've got to keep pushing that door open and working to ensure that those desperate people get the help that they need."
US Secretary of State Condoleezza Rice said the responsibility for the situation lay with the Burmese government.
"It's a quite unusual situation actually that you have a country in this desperate straits with its population in the circumstances that this population is in - and you get a kind of stone cold face about people who just want help," she told the BBC.
The UN estimates that only a quarter of the 2.5 million Burmese affected by the cyclone have received the help they need.
The Red Cross has said that in districts further south-west of those shown to Mr Ban, waterways were still clogged with corpses and that many people had received no aid.
One foreign doctor told the BBC many were drinking water from puddles, while children and old people were suffering from dysentery, dengue fever and dehydration.
Inside a camp for homeless cyclone survivors in Labutta
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