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As world governments and private organizations increase their financial pledges for the tsunami (search) disaster in Asia, the United Nations is stressing that billions will be needed in the long-term.

U.N. Secretary-General Kofi Annan (search) says he's "satisfied" with world government relief pledges for victims of the tsunami, but he stressed that U.N. resources are stretched thin and long-term aid is needed.

Around $500 million has been pledged so far, including a $250 million commitment from the World Bank (search), Annan said Thursday. "This is an unprecedented global catastrophe and it requires an unprecedented global response," he said.

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"Over the past few days it has registered deeply in the consciousness and conscience of the world as we seek to grasp the speed, the force and magnitude with which it happened. But we must also remain committed for the longer term," he said.

Annan said countries would need to coordinate and pool efforts, because no one country or agency could deal with the disaster alone.

Annan applauded U.S. efforts to set up a core planning group, which includes Japan, India, Australia and the United Nations.

Annan was to meet with Secretary of State Colin Powell at the United Nations on Friday to discuss relief efforts.

Annan met with European Union ambassadors to the United Nations on Thursday. Afterward, Ambassador Dirk Jan van den Berg of the Netherlands, which holds the European Union presidency, said he expected the European Commission to join the core group.

Citing the scope of the disaster, which involves tens of thousands dead and millions in need of immediate assistance, Annan said more helping hands are needed.

He said he hoped the donor nations will not use development aid as relief funds, "robbing Peter to pay Paul."

U.N. humanitarian chief Jan Egeland said Thursday the U.N. appeal for emergency relief to be launched Jan. 6 would be in the hundreds of millions of dollars, but long-term costs would be higher.

"The reconstruction effort will be just tremendous and the total damages in the billions and billions of dollars," he said.

While acknowledging that global response has been generous, Egeland reiterated his concern that rich nations give too little for long-term development assistance.

"I am not satisfied with the many rich countries in the world who are getting increasingly rich ... . It is my full-time job to advocate for the poor and to ask for more money from those who can give."

Echoing Annan's comments, Egeland also said the United Nations is "overstretched" because of crises in Sudan and Congo.

"In Eastern Congo we have surveys saying 1,000 people die per day from preventable disease and from humanitarian neglect," he said. "That is a tsunami every four months, for years. We do not have enough resources."

Several countries made new aid commitments Thursday.

France roughly doubled its aid pledge to $57 million, and Britain tripled an earlier relief donation to $95 million.

Canada has pledged $33 million. Sweden pledged $75 million.