The morning plenary session of the 2012 Seoul Nuclear Security Summit started in Seoul, March 27, 2012. [Photo/Xinhua]

SEOUL -- The morning plenary session of the 2012 Seoul Nuclear Security Summit started in Seoul Tuesday morning, with leaders and representatives from more than 50 nations and four international institutions discussing the response to nuclear terrorism, protection of nuclear materials and facilities as well as prevention of illegal trafficking of nuclear materials.

Giving an opening remark at the beginning of the session, South Korean President Lee Myung-bak stressed the need for close international coordination to strengthen the global nuclear security regime

"I expect the Seoul summit, building upon the achievements made at the Washington summit, to take a step further in generating a consensus and action plans," Lee said.

Noting 1,600 tons of highly enriched uranium and 500 tons of plutonium capable of producing some 126,500 nuclear weapons are stored worldwide, Lee said minimizing and ultimately removing all loose nuclear materials is a fundamental solution for preventing nuclear terrorism.

Lee continued that it is the obligation of world leaders to maintain peace and security of all mankind. Therefore, they must carry out all means to prevent terrorists from obtaining nuclear materials.

President of the United States Barack Obama said more nations come to the summit "not to talk but to take actions".

The world's governments are fulfilling commitments made in Washington, removing nuclear materials, making more real, tangible steps. More nations come to the table, not to talk but to take actions, said Obama.

"I think we all understand that no one nation can do this alone, and the goal will only be met when we work as an international community. What we did in Washington and what we do in Seoul will be part of a larger global architecture designed to reduce the threat of nuclear terrorism and pursuing peaceful uses of nuclear technology," he said.

The plenary session will be held for two and a half hours, followed by a working lunch and another plenary session before Lee holds a press conference highlighting the achievements of the two- day summit.

The Seoul communique, to be announced on Tuesday, is expected to reaffirm the international commitments to minimizing the use of highly-enriched uranium and plutonium and expand discussions on nuclear safety in the context of nuclear security following the tsunami-triggered nuclear crisis in Japan.