President Barack Obama has set the goal of eventually ridding the world of nuclear arms as a central theme of his presidency, but North Korea's defiance and other recent setbacks have raised fresh doubts about whether he can turn his vision into reality.
With Obama's broader nuclear agenda seemingly imperiled at home and abroad, he now faces a test of whether he can salvage credibility for U.S. leadership in dealing effectively with more immediate threats like the one posed by Pyongyang.
North Korea has suddenly jumped to the top of Obama's list with the disclosure of new advances in uranium enrichment at its main atomic complex and its shelling of a South Korean island on Tuesday.
Obama's is expected to try to balance hard rhetoric to intimidate and contain the North with diplomacy aimed at avoiding military escalation as he seeks to rally the international community to ratchet up the pressure on the reclusive communist leadership in Pyongyang.
Some analysts question whether such a nuanced approach will be enough to bolster his longer-term push for global nuclear disarmament.
Those hopes have already suffered setbacks as Iran continues to flout international demands to curb its nuclear program and Obama's signature arms reduction treaty with Russia remains bogged down in the U.S. Senate.
Obama set expectations high last year in Prague when he declared it was time to end "Cold War thinking" and committed the United States to seeking a nuclear weapons-free world.
Obama followed in April with the unveiling of a new U.S. policy that renounced development of new nuclear weapons and restricted use of those already in Washington's arsenal.
Aides said it set an example for other nuclear nations, which just days later attended a nuclear security summit hosted by Obama at which he secured agreement to work toward locking down loose bomb-making material.
But the new U.S. doctrine drew condemnation from conservatives who said it would compromise national security.
Critics say Obama's approach has also helped embolden Iran and North Korea, which have largely spurned Obama's diplomatic outreach and pressed ahead with their nuclear programs.