President Barack Obama, right, meets with Nigeria's acting President Goodluck Jonathan, left, in advance of the Nuclear Security Summit, at Blair House in Washington, Sunday, April 11, 2010. (AP Photo/Pablo Martinez Monsivais)
WASHINGTON (AP) - The formal meeting portion of a 47-nation nuclear summit takes place today in Washington with an optimistic President Barack Obama scheduled to deliver remarks.
He's gotten a boost by Ukraine's announcement that it will give up its weapons-grade uranium. Obama also met separately with China's leader to discuss worries about Iran's nuclear program.
The leaders are discussing a plan to secure all vulnerable nuclear materials worldwide within four years. The goal is to keep those materials out of the hands of terrorists.
Obama's counterterrorism chief warns that al-Qaida is vigorously pursuing material and expertise for a bomb.
Presidential aides say this is the largest gathering of world leaders hosted by an American president since the 1945 conference that founded the United Nations.