Various threats to be covered at Nuclear Security Summit

Dozens of world leaders assembling on Friday for the final day of nuclear security summit will confront a disparate array of modern-day threats, ranging from countries like North Korea to nongovernmental groups like DAESH.

The summit held in Washington, DC is President Barack Obama's last major push on denuclearization. Though Obama planned to show the Iran nuclear deal as evidence of progress, the absence of key players -especially Russia- underscored the lack of unanimity.

After six years of prodding by Obama, the global stockpile of fissile material that could be used in nuclear bombs remains in the thousands of metric tons. Security officials also warn that the radioactive ingredients for a "dirty bomb" are alarmingly insecure in many parts of the globe.

"We have not only great urgency around the nuclear issue, but eliminating generally the scourge of terrorism," Obama said during a meeting on Thursday with French President Francois Hollande, as he reflected on recent attacks in Brussels and Paris.

Ahead of the summit, less than half of the participating countries had agreed to secure their sources of radiological material, readily available in hospital, industrial and academic settings. Concerns about substances like cesium or cobalt getting in the wrong hands have grown following deadly attacks by DAESH.

There will be a special session on Friday to focus on the threat posed to major urban areas by terror groups which the US says are on the hunt for nuclear materials.

As the summit opened Thursday, leaders trained their focus on North Korea, whose continued provocations have stoked concerns throughout the region. Obama discussed steps to deter further North Korean missile tests during a meeting with Chinese President Xi Jinping.

In another session with the leaders of Japan and South Korea, he called for vigorous implementation of stepped-up UN sanctions.

Russian President Vladimir Putin, whose massive nuclear weapons stockpile is rivaled only by the US, refused to attend this year's summit. Moscow scoffed at what it deemed US efforts to control the process and take power away from international agencies.