U.S. President Barack Obama will open Monday an unprecedented Nuclear Security Summit of 47 nations to focus on global action to secure nuclear materials and keep them out of the hands of terrorists.

The White House says the final communiqué to be issued on Tuesday will formally recognize the serious threat posed by nuclear terrorism, endorse efforts to secure all vulnerable nuclear materials over a four year period and speak about what countries will do on the national and international level.

Iran and North Korea were not invited whereas British Prime Minister Gordon Brown will not be attending because of election campaign.