US President Barack Obama has warned that terrorists still had the ability to seize nuclear materials to carry out the most devastating type of attack against civilians. 
"One of the greatest threats to global security," Obama said is "terrorists getting their hands on a weapon of mass destruction."  The effort to secure nuclear materials is "by no means finished," he warned in is Saturday weekly radio address on the last day of the sixth Nuclear Security Summit. 
"significant and meaningful" progress had nevertheless been made at the summit to secure enough nuclear stockpiles to make 150 weapons,' Obama Added. 
Other progress at the summit included protecting nuclear facilities from cyberattacks and increasing intelligence sharing among nations to keep nuclear materials out of the hands of terrorists. 
Some unconfirmed reports indicated that Islamic State operatives had tried to enter a nuclear power plant at the time of the terrorist attacks in Brussels last month. As many as 12 nations had completely disposed of their supplies of enriched uranium and plutonium in the past years, Obama said. 
"This is a perfect example of a 21st-century security challenge that no one nation can solve alone," Obama said at the summit. "It requires coalitions and sustained coordination across borders and institutions. And the good news is we’ve made significant progress." Fifty world leaders gathered in Washington for three days for what could be the last nuclear summit, which was instituted by Obama six years ago. It isn't known whether the next US president, to be elected in November, will carry on the tradition.

Source: QNA