Earlier this month, Preval and several government officials issued conflicting figures on the number of people killed, ranging from 170,000 to 270,000, with the largest figured put down to "a typing mistake".
With no foreign government or independent agency issuing its own death toll, the confusion highlighted scepticism over whether the Haitian government's figures were accurate.
Donors have already pledged $673m in aid for Haiti and the UN has increased the size of its appeal to a record $1.5bn to help Haitians displaced by the quake.
|Disaster experts say slow pace of clearing rubble could trigger spread of diseases
But Preval pleaded for more aid on Sunday – his appeal topping the agenda at the regional summit being held near the Mexican resort town of Playa del Carmen.
With 250,000 houses destroyed and 1.5 million people living in tent camps made with bed sheets and plastic scraps in nearly every open space in the collapsed capital of Port-au-Prince, the most urgent need was for emergency shelter, Preval said.
"The first rainy days that have started falling in Port-au-Prince have made it impossible to enjoy a dignified life and this is the reason for the request for shelters," the president said.
Aid workers worry that squalid conditions in the camps, many of which still have no latrines or clean water, could lead to disease outbreaks when the rainy season begins in earnest in a few weeks.
And disaster specialists told Al Jazeera that the slow pace of clearing rubble and the decomposing bodies underneath, could trigger the spread of diseases such as typhoid and cholera and lead to even more deaths.
Preval also encouraged Latin American countries to step up investments in industry to help Haiti free itself from dependence on international aid.
Looking ahead to a meeting with international donors to determine the overall shape of rebuilding plans, he suggested Haiti should decentralise away from Port-au-Prince, which suffered the heaviest damage.
"We will not try to reconstruct but rather to refound the country, where we don't concentrate ourselves in one capital," he said.