Washington and Seoul have reached a deal for the sale of GBU-28 bombs, used during the 1990-91 Gulf War to destroy Iraq's underground command centers, a South Korean Defense Ministry official told AFP on condition of anonymity.

The laser-guided bombs will be delivered to South Korea between 2010 and 2014, South Korea's Yonhap news agency reported.

To confront Pyongyang's much-feared artillery if a war breaks out, South Korean jet fighters will carry the bombs and target underground sites such as North Korea's nuclear and artillery facilities, allegedly hidden in caves and tunnels.

In April, top US commander General Walter Sharp claimed that the North had the world's largest artillery force, with its artillery pieces deployed along the border numbering up to 13,000.

The United States has been Seoul's main supplier of war equipment and has retained nearly 28,500 troops stationed in the Asian country since the 1950-53 Korean War.

Tensions have mounted between the two Koreas after the North tested a nuclear weapon and fired six short-range missiles last week, drawing international condemnation.

The Communist government in North Korea insists that it intends only to reinforce its nuclear "deterrence" against the United States and its allies in the Korean peninsula.