国际英语新闻：Nuclear security summit kicks off in U.S. capital

According to White House officials, Tuesday's plenary session in the morning will be focused on national actions countries can take to secure nuclear material under their control and to deal with the risk of nuclear smuggling within their territory.

They have voiced expectation that some countries will announce steps they are taking to either remove the presence of some nuclear materials on their territory or to consolidate them to protect them better, such as the pledge to remove weapons grade uranium made by Ukraine.

After the morning session, another plenary session will follow in the afternoon. Since the morning session will be focused on actions countries can take on a national level, the afternoon session will be focused on international measures that countries can take to strengthen the international system for dealing with nuclear security.

Soldiers stand guard outside the Washington Convention Center prior to the Nuclear Security Summit in Washington, capital of the United States, April 12, 2010.

Obama was optimistic in securing the endorsement of the world leaders for his vision.

He said the level of world leader participation in the summit is "an indication of how deeply concerned everybody should be with the possibilities of nuclear traffic."

"I think at the end of this we're going to see some very specific, concrete actions that each nation is taking that will make the world a little bit safer," he told reporters before the welcome ceremony.