Full coverage: Xi Visits Czech Republic, Attends Nuclear Security Summit

A US official at the nuclear summit spoke highly of China's contribution to nuclear security. Myles Gaggins, assistant press secretary of the White House National security council, said cooperation among countries on nuclear security will continue after the summit. 

"We will establish nuclear security working groups with experts from each country that participated in the nuclear security summit. So we will continue the cooperation both cross borders and through international agencies to ensure that nuclear materials are safe. Safe in commercial uses, safe from getting into the hands of terrorists. And that work will continue many years. We've already seen cooperation between China and United State on nuclear security," said Myles Gaggins, assist. press secretary of the White House National Security Council.

"For instance this March, China established the nuclear security center of excellence. And China has sent representatives at nuclear security exercises hosted by the US department of energy. This cooperation will continue beyond the Obama administration to many years in the future."