Obama Warns Threat Of Nuclear Terrorism Rising

U.S. President Barack Obama (left) greets his Russian counterpart Dmitry Medvedev at the Nuclear Security Summit in Washington on April 12.

U.S. President Barack Obama has warned that the threat of terrorists using a nuclear weapon has risen.

Obama said that already "terrorist networks such as Al-Qaeda have tried to acquire the material for a nuclear weapon." He called on countries to adopt a "concrete" plan to secure nuclear materials within four years.

During the summit, Ukraine and Canada announced plans to give up highly enriched uranium and produce much safer, lower-enriched uranium instead.

U.S. Secretary of State Hillary Clinton and Russian Foreign Minister Sergei Lavrov are expected to sign a deal today to implement an agreement for the two countries to each dispose of 34,000 metric tons of weapons-grade plutonium.

Leaders and top officials from more than 47 countries are attending the summit, the largest hosted by a U.S. president since 1945.

Obama announced plans for a follow-up summit to be hosted by South Korea in 2012.

compiled from agency reports