BANDA ACEH, Jan 5: US Secretary of State Colin Powell saw the devastation of tsunami-hit Asia on Wednesday and found it more horrible than the war he had witnessed during decades as a soldier.

As Mr Powell got a bird's-eye view of the broken coastal landscape of Sumatra, world leaders began gathering in Indonesia's capital Jakarta for Thursday's summit on rebuilding the millions of lives shattered by the giant waves 10 days ago.

Australia and Germany dramatically pledged more than a billion dollars in aid to the region. A debt relief initiative by rich nations gathered momentum. Mr Powell promised the United States would send more helicopters, food and clean water to isolated survivors of the disaster that killed more than 145,000 people. Last week Washington was accused of being too slow to react.

"I have been in war and I have been through a number of hurricanes, tornados and other relief operations, but I have never seen anything like this," America's former top soldier said.

Mr Powell, 67, served two combat tours in Vietnam during a 35-year military career that ended with his service as the country's military chief. "I cannot begin to imagine the horror that went through families and all of the people who heard this noise coming and then had their lives snuffed out by this wave," he said.

After a helicopter tour, Mr Powell left for Jakarta, where UN Secretary General Kofi Annan and other world leaders were arriving for Thursday's global relief summit for tsunami-hit Indonesia, Thailand, Sri Lanka, India, Maldives and Malaysia.

Mr Annan called on world leaders to honour their pledges of aid, saying it should be "fresh and additional money, not robbing Peter to pay Paul, pulling it from other crises".

International aid groups echoed Mr Annan's call. "We must ensure we don't repeat mistakes of previous humanitarian crises in Afghanistan, Liberia and else where donors have either failed to deliver the aid quickly enough, or at all, or delivered aid at the expense of other disasters," said Barbara Stocking, director of Oxfam.

DEBT RELIEF: Mr Annan was expected to announce a UN tsunami appeal at the Jakarta conference, which would also discuss the possibility of an immediate freeze of debt payments by affected countries.