Germany says it is increasing its aid pledge tsunami victims to more than 500m euros (£352m or $661m).
Germany is increasing its pledge from $27m to $674m
This makes Germany the biggest European donor to the relief effort for Asian countries hit by the disaster.
Meanwhile, UK Prime Minister Tony Blair said his country was ready to increase its pledge from £75m ($140m or 106m euros) to several hundred million.
He said the UK would also join a conference to discuss the cancellation of the affected countries' debts.
The German Chancellor Gerhard Schroeder, who announced his country's increase in aid on Wednesday, also backed calls for leading industrial nations to examine debt relief.
"The cabinet decided today to commit 500m euros, and over a period of not less than three years and not more than five years," he said.
The BBC's Ray Furlong says Germany is already struggling to get its budget deficit below limits set by the EU's Stability Pact for countries using the euro.
But Mr Schroeder dismissed any doubts about the aid, saying the money would be found within the existing budget plans for 2005 and following years.
The new pledge comes as Germany lobbies for a permanent seat in the UN Security Council. But Mr Schroeder denied any link between that campaign and the aid.
Senior representatives from 26 nations are expected to take part in the donors' conference that opens in the Indonesian capital, Jakarta, on Thursday.
Participants will focus on co-ordinating the aid and recovery efforts.
UN Secretary-General Kofi Annan and US Secretary of State Colin Powell have already arrived in Indonesia.
In the list of major donors, Germany is second only to Australia, which announced that it was planning to provide A$1bn ($764m or £406m or 577 m euros).
Germany is followed by Japan which has pledged $500m (£266m or 378m euros), followed by the US with $350m (£186m or 264m euros) and Norway with $181m (£96m or 136m euros).
The World Bank has pledged $250m (£133m or 189m euros).
Almost all EU members, including many eastern European governments, have allocated millions of dollars to help countries in the disaster zone.
Germany is also the leader in private donations, having collected more than a third of the world's total.
It is followed by Britain where private donations exceed government pledges by almost 50%.