Published: Apr 13, 2010 9:53 PM EDT

 WASHINGTON - President Barack Obama says Americans are safer and the world is more secure as he closed a two-day conference on nuclear security.

On Tuesday, Obama wrapped up a 47-nation summit in downtown Washington with a general agreement to secure all the globe's vulnerable nuclear materials within four years.

Obama says the leaders seized the opportunity to take action to make certain nuclear material never falls into the hands of terrorists.

Leaders from around the globe pledged to turn over nuclear material to the United States and close some nuclear reactors. Obama says the United States would strengthen security at its own nuclear sites and allow international inspections.

Related: Obama says risks of nuclear attack have risen