The conference was opened by Indonesian President Susilo Bambang Yudhoyono, whose country was hardest hit by the 26 December undersea earthquake and ensuing giant waves.
Yudhoyono called for an unprecedented effort to overcome the suffering.
"Our response to this unprecedented catastrophe must be equally unprecedented so that we can immediately put an end to the human suffering and misery that came after," Yudhoyono said. "Many today are in danger of dying of diseases, hunger and trauma. The death tolls must not be allowed to rise any further."
Speaking at a summit news conference, UN Secretary-General Kofi Annan said the international community has solidly backed the United Nations with its response to the disaster. Governments, corporations, and private individuals have pledged between $3 billion and $4 billion in assistance.
"The world has come together, and we are working together," Annan said. "The spirit at the conference and the spirit in the room and my discussions with the leaders who are here lead me to believe that we are responding and there is solidarity and we are going to really make a difference here."
Germany and Australia announced major increases in their aid pledges, to more than $650 million each. Japan is giving $500 million, and the United States $350 million, plus the logistic services of naval and air forces.
Annan called for countries to quickly honor their aid commitments, saying swift action is needed to stop a second wave of deaths from starvation and disease. He said nearly $1 billion is immediately needed to cover emergency humanitarian needs over the next six months for some 5 million survivors.
Japan responded to the UN's appeal by announcing it will provide $250 million of its tsunami relief funds no later than March.
Speaking in Berlin, German Chancellor Gerhard Schroeder emphasized that the aid effort must look well beyond the immediate tragedy.
"Despite the importance of this immediate help, it is not enough," Schroeder said. "I have tried from the beginning to make clear that the solidarity which exists in Germany needs to be incorporated into a medium-range and long-term program. The cabinet has, therefore, decided today to make available 500 million euros within a time frame of not under three years and not above five years."
Japanese Prime Minister Junichiro Koizumi also told the summit that Tokyo is willing to grant a debt moratorium to countries hit by the disaster, and he asked other lenders to do the same.
The United States, Britain, Canada, and France already support a debt moratorium. The subject will be discussed at a meeting of the so-called Paris Club of creditor countries on 12 January.
At the Jakarta summit, the leaders also discussed setting up a tsunami warning system for the Indian Ocean to avert a similar catastrophe in the future.