Ban Ki-moon meets victims of the Haiti quake
Ban Ki-moon has offered assurances of the world's continued commitment to help Haiti.
The United Nations secretary general stressed providing shelter was the top priority as he made his second visit to the stricken country.
Hundreds of thousands of people remain in urgent need, two months after the magnitude-7.0 earthquake.
Mr Ban first visited Haiti soon after the devastating quake, which killed more than 200,000 people.
During his one-day visit, Mr Ban toured a makeshift camp of more than 40,000 people and also met with Haiti's President, Rene Preval.
Once a golf course, the camp is now covered in blue, orange and white tarps and tents.
Mr Ban said his message to Haiti's government and people is that the world will not forgot.
"The world is always at their side," he said.
AT THE SCENE
Mark Doyle, BBC News, Port au Prince
The golf course full of homeless people is a bizarre and tragic sight.
Ban Ki-moon walked one of the fairways where there are now thousands upon thousands of flimsy tents and tarpaulins.
Crammed together are men, women and children still trying to survive the impact of the earthquake.
The shelter is inadequate, the sanitation is poor, and for these people who are also psychologically traumatised, there is no privacy, little dignity.
Speaking at a news conference, Mr Ban acknowledged that Haiti needs money for schools, infrastructure, roads, ports and electricity.
The quake on 12 January left more than a million Haitians homeless.
The prospect of the heavy rainy season, due to start soon, is increasing concern.
Mr Ban said 60% of Haiti's quake homeless have received plastic sheets or tents to protect them from deluges.
But he admitted more needed to be done.
"We are a little bit behind schedule, but we are moving very quickly," he said.
Mr Ban added there needed to be a more efficient way of distributing emergency shelter.
A high-level UN donor's conference for Haiti is taking place at the end of this month in New York.
Mr Ban pledged to try and keep donor funds flowing, describing the world's response so far as "extraordinarily generous".
But he noted the UN's revised emergency Haiti appeal, totalling $1.4bn (£0.9bn) this year, was only 49% funded so far.
Mr Preval said his country must start looking to the longer term and think about its future economy.
He highlighted concerns that Haiti's farmers would be hurt by continuing imports of food aid.
"It was absolutely necessary that international aid arrive after the earthquake," Mr Preval said.
But he added: "We are now in a new reality."