The US$717 million was an 'extraordinary effort' and the most the United Nations had ever collected for a catastrophe, said Jan Egeland, UN undersecretary-general for humanitarian affairs.

Humanitarian and development aid experts were just as surprised, although doubtful about whether the billions more pledged would materialise so readily.

More than US$8 billion has so far been given or promised worldwide, about half from public donations to charities and the remainder by governments. It is the latter amounts announced by politicians that are of concern to observers.

Canadian development consultant Ian Smillie, who has 30 years' experience in aid work, said yesterday that there were significant differences in announcements, pledges and commitments. 'There are a lot of announcements being made and a lot of numbers thrown around, but few of them will translate into any hard pledges.'

His view was backed by a senior researcher with the Overseas Development Institute in London, Edward Clay, who described some pledges by politicians as 'window-dressing rather than reality'.

'They say it's new money even though it has often been reallocated from one government funding area to another,' Dr Clay explained. 'All politicians do this. Often, this is quite explicitly done, although sometimes it's done with the best of intentions to get the money quickly,'

Charities have expressed concern about the practice, which they claim will lead to humanitarian needs in other parts of the world - especially Africa - being neglected or ignored.

The difference between announcements and committed funds was highlighted last weekend by Iran's President Mohammad Khatami, who claimed that just US$17.7 million of the US$1 billion promised for the December 26, 2003, earthquake in the Iranian city of Bam had been received.

Stephanie Bunker, of the UN's Office for the Co-ordination of Humanitarian Affairs, said such situations were not unusual.

Paradoxically, though, like the tsunami appeal, a pledging conference for the western Sudanese region of Darfur had been more successful, with most pledges translating into specific commitments.

Ms Bunker was hopeful that given the overwhelming media and public response to the tsunami disaster, in which 158,000 people have lost their lives, promises by governments would be kept.

'The best we can do is keep following up with the donors,' she said. 'We can hope that with meetings and similar follow-up, we will continue to get a good response.

'Ultimately though, any questions will have to go back to the donor governments from citizens and the media.'

Such attention led to massive global help in 1970 for victims of the Biafran civil war in Nigeria and a cyclone in Bangladesh and in 1984 for famine relief in Ethiopia.

Mr Smillie said western governments were now generally committed to the idea of allocating 0.7 per cent of their annual gross national product to foreign aid - although few actually did.

'Apart from the Scandinavians and Dutch, none do,' he said.