WASHINGTON (Reuters) – Criminal gangs have duped  al Qaeda with offers of bogus nuclear material, hampering the  group’s efforts to build a nuclear bomb that would allow them  to “threaten world order,” the White House said yesterday.

“There have been numerous reports over the past eight or  nine years of attempts to obtain various types of purported  material,” John Brennan, President Barack Obama’s  counter-terrorism adviser, told reporters.

“We know al Qaeda has been involved a number of times. We  know they have been scammed a number of times,” Brennan said on  the sidelines of a 47-nation summit aimed at preventing nuclear  material falling into the hands of terrorists.

Brennan said there was “strong body of evidence” that al  Qaeda had made it a top priority to acquire the expertise and  separated plutonium or highly enriched uranium needed to build  a nuclear bomb.

Obtaining such a bomb was the “ultimate and most prized  goal” of terrorist groups, who were also seeking radiological,  chemical and biological weapons, he said. US officials acknowledge, however, that the United  States’ concerns about the threat of nuclear terrorism are not  shared by all countries.

The aim of Obama’s summit is to persuade countries,  particularly those with stockpiles of weapons-grade nuclear  material, that the threat is real and growing and that steps  must be taken within four years to secure the material.

“We cannot wait any longer before we lock down these  stockpiles,” Brennan said.

“Disturbingly, organized criminal syndicates are keenly  aware of terrorist groups’ interest in nuclear weapons.”