GENEVA -- Halfway through 2013, the world already needs to spend more than twice what it did last year, if it wants to help all the 73 million people who are suffering in Syria and other major crises around the world, the U.N. top humanitarian official said Wednesday.

As much as $12.94 billion is needed, more than has ever been requested in any year before, and that figure represents only the needs that are known at the midpoint of this year, so it will continue to go up, according to Valerie Amos, the U.N. undersecretary general for humanitarian affairs and emergency relief.

That compares with the $9.71 billion that the U.N. sought for all of last year of which donors provided just 63 per cent, or $6.1 billion.

So far donors have provided $5.1 billion, or about 40 per cent of the "unprecedented" needs this year, Amos said.

But that is roughly the same amount that the United Nations said was needed for all of 2007 -- and donors only provided 72 per cent of the $5.14 billion request five years ago.

"In a normal year, that would be a huge statement to the commitment to humanitarian action," Amos told reporters in Geneva of the $5.1 billion raised so far that has gone to people in 24 countries, including Syria, Niger, Sudan and Afghanistan. "But this is an extraordinary year."

The Syrian civil war that's spilling into the region is taking up as much as a third of the needs this year.

Amos, a baroness and British lawmaker who heads the U.N. Office for the Coordination of Humanitarian Affairs, said Syria requires at least $4.4 billion in aid for the 6.8 million people who are suffering inside the war-torn country and the 5.3 million refugees or others who are affected by the conflict in border nations.

She conceded she had "no idea" how to get the rest of the money that is meant to pay for the year's collective humanitarian work of 620 U.N. and affiliated aid agencies.

Adding to the challenge is that global humanitarian aid more broadly fell 8 per cent last year to $17.9 billion, down from $19.4 billion in 2011, according to a separate report Wednesday from the British-based anti-poverty organization Development Initiatives. The organization measures global needs, not just those of the U.N. and affiliated aid agencies.

Donors could save money if they responded to crises sooner or spent more on development and other ways of cutting the risk of conflicts, said Judith Randel, the executive director of Development Initiatives.

The biggest previous U.N. request was in 2010 for $11.25 billion -- which was only 64 per cent funded -- to deal with the Haiti earthquake, Pakistan's floods and other major crises.

But the likelihood is that as much as a third of what the United Nations says is needed this year won't be raised, according to the U.N.'s own figures.

Over the past five years, the United Nations has only been able to scrounge up between 63 per cent and 72 per cent of what it says is required to feed, house and provide other help to the millions of people trying to survive often desperate conditions, the figures show.

Going back to 2000, the trend looks even bleaker, with the level of U.N. funding requests that have been filled ranging from 55 per cent to 72 per cent, according to an analysis by Development Initiatives.

"Halfway through the year, we know that 73 million people need humanitarian assistance," Amos said. "The increase is largely due to the exploding crisis in Syria, and the neighbouring region, but also because situations have worsened in other countries like the Central African Republic and Mali."