NUCLEAR SECURITY SUMMIT

As heads of state gathered for talks, demonstrators chanted: No nukes Asia, no nukes Korea, No nukes [America], no nukes anywhere! Many cited the disaster at power plants hit by the March 2011 earthquake and tsunami in Japan as proof of nuclear power's inherent risks.

Australia has blocked China's Huawei Technologies Co Ltd HWT.UL from tendering for contracts in the country's $38 billion National Broadband Network (NBN) due to cyber security concerns, Huawei said on Monday.

Leading up to the nuclear summit in South Korea this week, Obama and Hu both expressed their serious concern about the launch, which was first described by North Korea as a peaceful launch of an earth observation satellite.

South Korea wrested one-upmanship from the belligerent North on Monday by issuing a stern warning that it might shoot down a rocket that Pyongyang is planning to launch next month.

Obama holds out prospect of cuts in US nuclear arsenal as he tries to rally world leaders against threat of nuclear terrorism.

Obama traveled to a US military base located at the edge of the 2.5 mile wide DMZ and greeted the soldiers there, as a symbolic reassurance of its support to South Korea.

President Obama was en route to South Korea Saturday for a two-day international nuclear security summit in Seoul as North Korea prepares to launch a satellite into space via rocket in April.

North Korea has warned it won't tolerate any criticism on its planned satellite launch. North Korea has threatened the critics of its nuclear weapons program that any denigration would be considered a declaration of war, New York Times reported.

Pyongyang officials said such rhetoric may be akin to a declaration of war.

The U.S. would like to ultimately recharge talks on disarmament, a process that would involve as total of six nations -- North Korea, South Korea, U.S., China, Russia and Japan.