Obama: ISIS Getting a Nuke 'Would Change Our World' Obama asked world leaders to tighten security on nuclear materials By Michael Harthorne, Newser Staff Posted Apr 1, 2016 3:39 PM CDT 318 comments Comments President Barack Obama arrives for a group photo with other world leaders during the Nuclear Security Summit Friday in Washington DC. (AP Photo/Alex Brandon) (Newser) – At a nuclear summit attended by more than 50 world leaders Friday in Washington DC, President Obama called the possibility of ISIS getting its hands on a nuclear weapon "one of the greatest threats to global security," the BBC reports. “There is no doubt that if these madmen ever got their hands on a nuclear bomb or nuclear material, they would certainly use it to kill as many innocent people as possible,” Obama said, per Reuters. “It would change our world.” It was part of Obama's pitch to world leaders to better secure their nuclear materials, which he said is the most effective way of keeping them from falling into the hands of terrorists. He also called on countries to stop stockpiling nuclear weapons. Obama said both al-Qaeda and ISIS are still seeking nuclear material for weaponizing, and the risk of nuclear terrorism remains very real. He pointed out recent news that ISIS members had been following a Belgian nuclear plant's senior manager and secretly recording his daily activities. "We cannot be complacent," he said. In addition to ISIS and al-Qaeda, world leaders also expressed concern with North Korea's nuclear weapons program. US officials estimate there is approximately 2,000 metric tons of material worldwide that could be used to build a nuclear weapon, NBC News reports. The US and Russia (Putin refused to attend the summit) account for 90% of the world's nuclear weapons with more than 14,000 nuclear warheads between them.