International efforts to cut off funding to al-Qaeda have made it more difficult for the terror network to operate, a top US official has said.
Terror attacks can be cheap, a UN report warned in August
Assistant Treasury Secretary Juan Zarate said some $150m in assets of al-Qaeda and former Afghan rulers the Taleban were frozen around the world.
He was speaking after briefing a UN committee monitoring sanctions against the two terror groups in New York.
A UN report said last year the al-Qaeda sanctions had been largely ineffective.
'Victim of own success'
"We think it is now harder, costlier and riskier for al-Qaeda to raise and move money," Mr Zarate told reporters.
"We've frozen now approximately $147m [£78m] in terrorist-related assets based on this process.
"The cornerstone of those efforts, frankly, has been our ability to designate individuals and entities who provide support for al-Qaeda and Taleban."
He did not identify which countries had seized or frozen funds belonging to the two groups.
UN sanctions also require all 191 members of the world body to impose a travel ban and arms embargo against individuals or groups linked to al-Qaeda and the Taleban.
However, Mr Zarate said the international community has become "a bit of a victim of its own success" in cutting off funding to terrorists.
He said that this "has led to an adaptation by terrorist groups like al-Qaeda to use more informal ways of moving and raising money".
Last year's UN report said that while al-Qaeda's access to funding had been curtailed as result of international co-operation, "so too has its need for money".
COST OF ATTACKS
Madrid bombings - less than $10,000
Bali nightclub bombings - less than $50,000
US embassy bombings in Kenya and Tanzania - less than $50,000
Attacks in Istanbul, Turkey - less than $40,000
9/11 attacks - "six figure sum"
"It is not clear from all reports of asset freezing, for example, what those assets are, their value, or who owns them," the report said.
It gave the example of the Madrid train bombings last March, in which nearly 200 people were killed by devices made from locally-available mining explosives, detonated by mobile telephones.
The report said that al-Qaeda had spent less than $50,000 on each of its major attacks since the 11 September 2001 hijackings.
Only the US attacks had required significant funding of over six figures, the report added.