Israeli Defence Minister Ehud Barak called on Wednesday for major powers to speed up efforts to stop Iran's nuclear programme, cautioning it would be tougher to confront it once Tehran managed to cross an atomic threshold.Israeli media interpreted Barak's comments as pushing for a possible Israeli strike against Iran to stop a project the West sees as a drive to achieve nuclear weapons though Tehran denies seeking nuclear weapons, saying its programme is intended solely for peaceful purposes."I am very well aware and know in depth the difficulties and complexity involved in preventing Iran from achieving nuclear weapons," Barak told a graduation ceremony for security officers, in remarks later released by his office."But it is clear to me beyond any doubt that confronting that (nuclear) challenge in itself once it ripens if it ripens, will be infinitely more complex infinitely more dangerous and infinitely more costly in human life and resources," he said."This is the time for the entire world to ready for united action, united goal in political desire in order to put a swift and definite stop to the Iranian nuclear project," Barak said.In his lengthy remarks, Barak said Israel now faced "its most complex challenges ever", adding "we may need to make fateful and difficult decisions with regard to Israel's security," pointing also to what he called growing instability posed by popular revolts in neighbouring Arab countries.