President Obama deserves praise for spearheading global efforts to address the threat of nuclear terrorism. As countries gathered for this week's Nuclear Security Summit in The Hague, it was clear that countries had made real progress in securing the world's most dangerous weapons.

This week's Nuclear Security Summit in The Hague was understandably overshadowed by the continuing international response to Russia's illegal annexation of Crimea. One aspect of the Ukraine crisis that deserves more attention is how the current standoff will impact the future of nuclear security cooperation between the United States and Russia.

World leaders called on countries on Tuesday to cut their use and their stocks of highly enriched nuclear fuel to the minimum to help prevent al Qaeda-style militants from obtaining material for atomic bombs.

Since the Rouhani administration reached its interim agreement with the world powers on Iran's nuclear program last November, the president's conservative rivals have faced a dual challenge. They fear a nuclear deal that will undermine the regime as a whole and, at same time, empower Rouhani's pragmatist faction.

Five years ago, President Barack Obama was preparing to deliver a speech in Prague calling for the elimination of nuclear weapons. Nongovernmental organizations, including the Stimson Center, helped with blueprints for getting to zero, and distinguished "formers" were lending their names to the cause. Now these initiatives seem like headlines from a bygone era. The pursuit of a world without nuclear weapons remains an essential complement to nuclear non-proliferation, but this quest cannot be divorced from international relations. President Obama continues to try to reduce nuclear dangers at Nuclear Security Summits and in negotiations with Iran, but progress comes grudgingly. The need of the hour is to prevent further backsliding, not to promote sweeping plans.

Prime Minister Shinzo Abe on Tuesday defended Japan's management of nuclear materials including weapons-grade plutonium, dismissing concern that a massive amount of nuclear substances could be used for non-civilian purposes.