The Seoul Nuclear Security Summit kicks off in just a few hours time. World leaders are in South Korea, hoping to reach a consensus on how to limit the spread of uranium and plutonium, used to make nuclear weapons. Many countries are becoming increasingly concerned that nuclear technology could fall into the hands of terrorist organizations.

South Korean President Lee Myung-bak (R) shakes hands with Chinese President Hu Jintao before their their meeting at the presidential house in Seoul March 26, 2012.

World Leaders have converged on Seoul to discuss what they see as an increasingly urgent agenda.

They hope to find an agreement on locking down fissile material that could potentially be used to build thousands of terrorist bombs.

The leaders from more than 50 countries including Chinese President Hu Jintao and US President Barack Obama and officials from international organizations will attend the summit.

Hu Jintao has already met with his South Korean counterpart Lee Myungbak to discuss international issues of common concern.

Speaking ahead of the summit, US President Obama voiced confidence that his country can further reduce its nuclear weapons stockpile, while managing to maintain its strategic deterrent and international security commitments.

At the top of the summit’s agenda, is how to control the spread of radioactive material, which is still freely available across the world.

Leaders will also focus on the link between nuclear security and nuclear safety, in the light of last year’s Fukushima disaster in Japan. Experts warn that the accident showed terrorists had the potential to sabotage nuclear power plants, by damaging cooling systems and cutting off power.

The Seoul gathering is the second Nuclear Security Summit, following the first talks in Washington in 2010. In a 2009 speech, US President Obama called nuclear terrorism "the most immediate and extreme threat to global security". He called on countries to secure all the world’s vulnerable nuclear material within four years.

Half way towards that four-year goal, and many nations have taken voluntary steps to limit the availability of material that could be used for terrorist weapons.

In a joint report, the Washington-based Arms Control Association and the Partnership for Global Security, which campaign against nuclear proliferation, acknowledged that major progress has been made.

Leaders will now look to go further, with the aim of reaching a broad international consensus that will bind nations on restricting the flow of nuclear material.