Obama says nuclear-armed N. Korea 'grave threat'

President Barack Obama said Tuesday that a nuclear-armed North Korea poses a “grave threat” to the world and cannot achieve its own security by building illegal weapons.

With South Korean President Lee Myung-bak at his side in the White House Rose Garden, Obama said they agreed that a new U.N. resolution seeking to halt North Korea’s development of nuclear weapons and ballistic missile must be fully enforced.