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* Nuclear terrorism seen as menace despite security progress
* IAEA meeting on July 1-5 to draw some 112 countries
* Draft ministerial statement short on specific measures
By Fredrik Dahl
VIENNA, June 24 (Reuters) - More than 100 states meeting next week will warn of the threat of nuclear terrorism but without deciding on any concrete new steps to counter the danger, a draft ministerial statement showed on Monday.
The document, which member states of the U.N. nuclear agency have been negotiating since March, looked unlikely to satisfy those who advocate stronger international action to ensure that potential nuclear bomb material does not fall into the wrong hands.
Still, Vienna-based diplomats said it would form a basis for future measures to improve global nuclear security, and stressed that the responsibility was mainly national.
To get all countries on board, "you are not going to have a document as ambitious" as some may have wanted, one envoy said.
Analysts say radical groups could theoretically build a crude but deadly nuclear device if they have the money, technical know-how and the amount of fissile material needed.
They say groups such as al Qaeda have been trying to get the components for such a nuclear bomb. Obtaining weapons-grade fissile material - highly enriched uranium or plutonium - poses their biggest challenge, so keeping it secure is vital, both at civilian and military facilities, experts and officials say.
Experts describe the threat of a crude fissile nuclear bomb - technically difficult to manufacture and requiring hard-to-obtain bomb-grade uranium or plutonium, as a "low probability, high consequence act" - that is, with the potential to cause massive harm to life and property.
On the other hand, a "dirty bomb", where conventional explosives are used to disperse radiation from a radioactive source, is a "high probability, low consequence act" with more potential to terrorise than cause large loss of life.
Diplomats say many countries regard nuclear security as a sensitive political issue that should be handled primarily by national authorities, and this was clearly reflected in the language of the ministerial statement.
MORE PROGRESS NEEDED
The statement, to be formally adopted at a July 1-5 conference hosted by the International Atomic Energy Agency (IAEA), said substantial progress has been made in the past few years to strengthen nuclear security, but that more is needed.
Ministers "remain concerned about the threat of nuclear and radiological terrorism and other malicious acts or sabotage related to facilities and activities involving nuclear and other radioactive material", said the document, obtained by Reuters.
IAEA Director General Yukiya Amano told Reuters last week that he saw "persistent risks" of nuclear terrorism. The information the U.N. watchdog receives about illicit nuclear-related trafficking may be the "tip of the iceberg", he said.
The international nuclear security regime "is not sufficiently robust" to protect against this kind of threat, an expert group said in a report this year.
An apple-sized amount of plutonium fashioned into a nuclear bomb and detonated in a highly populated urban area could instantly kill or injure hundreds of thousands of people, the Nuclear Security Governance Experts Group said.
"Preventing one of the world's major threats deserves bold action and new thinking," they added.
One of them, former Danish ambassador to the IAEA John Bernhard, said on Monday he believed the U.N. agency should have both more powers and resources to help enhance nuclear security.
U.S. President Barack Obama last week said he would host a summit in 2016 on securing such materials and preventing nuclear terrorism. He put on such a summit in 2010, a second was held in Seoul in 2012 and a third will be in The Hague next year.
Unlike those meetings, attended by leaders from around 50 countries, next week's conference in Vienna is open to all members of the 159-nation IAEA, which says it expects officials from some 112 countries as well as 20 organisations. (Editing by Mark Heinrich)