US President Barack Obama is hosting the fourth Nuclear Security Summit in Washington in the backdrop of rising fears over global terror organisations laying hands on nuclear weapons and nuclear rogues advancing their capabilities.
More than 50 heads of state will participate in the final edition of the nuclear summit, which Obama launched in 2010 as the signature campaign of his presidency.
The summit has been held every two years since then, with discussions focusing on the risks in civilian nuclear sector, apart from the reduction of warheads and non-proliferating efforts.
The summit is meant to "raise awareness of the risk of nuclear terrorism and to secure weapons-usable material in the civilian sector", says Kelsey Davenport, the director of Arms Control Association.
The summit's goals include tying up loose ends in nuclear safety such as securing the safety of weapons-usable nuclear materials, preventing non-state players from getting access to ingredients for making 'dirty bombs', ensuring on-site physical protection and securing nuclear materials and processes from online attacks.
The summit has highlighted over the years the lack of international protocols that legally bind countries to ensure the safety of their civilian nuclear materials.
The fears of nuclear materials spilling out in the open and becoming accessible to terror organisations are at the highest point after the sophisticated terror machine of the Islamic State (Isis) demonstrated the scope of their invasive network and capabilities.
Belgian media reported last week the Brussels suicide bombers might have considered attacking a nuclear site in the country after evidence showed they had gathered significant information about the daily routine of the head of the nuclear research programme.
Obama's nuclear security initiative's successes included the arms reduction treaty with Russia and the Iran nuclear deal but the challenge ahead is daunting.
"The Nuclear Security Summits have had a positive effect, but the strategic goal of developing an effective global nuclear security system remains unachieved," the Nuclear Threat Initiative, an anti-proliferation watchdog, said, according to Reuters.
The report also says nuclear reactors of many countries, including in China and Belgium, are still vulnerable to cyber attacks.
According to the Nuclear Security Index of the group, there has been little progress in the last two years in areas like on-site physical protection, security during transport and the ability to recover lost radioactive materials.
The final edition of the Nuclear Summit, which was inspired by a landmark speech on the topic by Obama in Prague in 2009, is hampered by the boycott of Russia and the absence of Iran at the discussion table.
Russia, one of world's biggest atomic powers, said there is a trust deficit that forces it from participating in the summit this time, referring to the differences with the US over Ukraine conflict.
Iran not invited
There has also been criticism over not inviting Iran, which recently signed a nuclear deal, to the summit, apparently over resistance from Israel and Saudi Arabia. The unwillingness of China to be part of any joint statements at various summits also points to the harder challenges Obama will this time.
Along with this, North Korea's recent nuclear test and aggressive military posturing adds to the concerns.
With less than 10 months left in office, Obama has a long way to go to burnish his credentials in nuclear non-proliferation and nuclear safety.
However, Obama officials exuded optimism before the summit started. Laura Holgate, Obama's adviser on weapons of mass destruction, said 30 countries that participated in the 2014 summit made substantial commitments.
"The international community has made it harder than ever for terrorists to acquire nuclear weapons, and that has made us all more secure," she said.