The October 8 earthquake, which killed more than 74,000 people, was "something the world could not have imagined," Annan told reporters after he was met at Chaklala Airbase by Foreign Minister Khurshid Mahmood Kasuri.
The UN chief is to attend a donors' conference on Saturday to raise money for the massive recovery effort, which UN and Pakistan agencies, the World Bank and the Asian Development Bank estimate will cost 5.2 billion dollars.
"I would expect ... those who have the capacity to be generous to give and give willingly and I am not only speaking to the governments, but also to the private sector and individuals, who have been generous," Annan said.
"We have received some response, but we need much, much more to be able to help the people in need," Annan said. "We need more resources, not just for emergency but also for recovery and reconstruction." President Pervez Musharraf has said the amount received so far was negligible.
Annan is due on Friday to tour parts of northern areas hit by the earthquake, which flattened entire villages in the Himalayan region and made more than three million homeless just before the arrival of winter.
There are fears of a second wave of deaths caused by the cold and disease, with outbreaks of acute diarrhoea already hitting some of the tent camps that are swelling as people come down from the freezing mountains.
Annan said some lives might have been saved if all the resources required to cope with the disaster had been available from the outset and it had been easier to funnel them into the remote and often inaccessible area.
"If we had been able to get all the resources, didn't have the logistical challenges that we have, some of the people that died may have been saved but it wasn't as bad as could have happened," he said.
Helicopters have been essential to the international rescue and relief effort that is still under way, with several roads and bridges destroyed in the quake which hit 7.6 on the Richter Scale.
Annan said devastated areas must be rebuilt so they could cope with another such quake.
"I hope we are going to rebuild better houses ... not just build what was before, but build it in a manner that can withstand, God forbid, another disaster, if it does come," he said.