In July 2005, the US Senate sanctioned $4 million to revive the Robust Earth Nuclear Penetrator (RNEP) research programme. Commonly known as "bunker busters", the RNEP is a significant nuclear-related measure contained in the Appropriation Bill for US fiscal year 2006. Their objective is to destroy deeply buried underground bunkers suspected of storing weapons of mass destruction. According to US Defence Secretary Donald Rumsfeld, the RNEP would revitalize the US nuclear weapons stockpile.

The US military community regards nuclear bunker busters as crucial, especially after its recent experiences in the 1991 Gulf War, and the war against the Taliban and Al Qeada forces in Afghanistan in 2001. The US-led forces faced great difficulties in finding the former Iraqi President Saddam Hussain, who was hiding in a bunker. Washington's inabilities and incapacities prompted the US Air Force to develop this earth- penetrating nuclear warhead.

Earth-penetration technology is a significant feature of US nuclear weapons programme. The first earth penetrator, Mark 8 was developed in 1952. Currently, the Pentagon possesses 50 upgraded nuclear bunker buster bombs known as B 61-11. According to the Bush administration, nuclear bunker busters are vital for eliminating deeply buried bunkers which could be storage sites for nuclear, biological and chemical materials or uranium-enrichment facilities. Bunkers are also used for housing communication centres for important military leaders. However, bunker busters have technical limitations that severely constrain their efficacy.

A RNEP has limited earth penetration capability. When a nuclear bunker buster is delivered by a short-range missile or a fighter aircraft it travels at high speed. But the moment it strikes the earth much of its impact is absorbed and it cannot penetrate more than a few feet. The B 61-11 nuclear earth penetrator can only penetrate 20 feet in dry soil. The target country could build its underground bunkers much deeper into the earth, thus reducing their susceptibility to a RNEP attack. In fact, any suspected underground storage site of WMD material can be destroyed by blocking the entrance of the tunnel with conventional explosives. This eliminates the need for nuclear bunker busters.

A RNEP would release considerable radiation. According to physicist Robert Nelson of Princeton University, a nuclear bunker buster needs to penetrate 230 feet deep into the earth to contain all radioactive fallouts. Established reports have confirmed that the B 61-11 can burrow only 20 feet into concrete. A larger fraction of radiation emitted from the bunker buster will surface up and drift into the atmosphere killing thousands of people and exposing millions to high risks of cancer. A RNEP would also cause massive collateral damage. Hypothetically, a RNEP warhead attack on an underground storage site beneath the Esfahan nuclear facility in Iran would result in the death of 3 million civilians in just two weeks. Radioactive fallout will be carried to Afghanistan killing 35 million people, and then reach Pakistan and India exposing millions to health hazards like cancer. The radioactive dust and debris contaminating the atmosphere over such vast territories will have serious ramifications.

Nuclear bunker busters constitute a threat to the non-proliferation regime. The US regards the RNEP as a militarily useful weapon intended to overcome its problems in a non-nuclear conflict. The nuclear bunker buster is designed to be a "usable" weapon, which obscures the distinction between conventional and nuclear weapons and lowers the threshold for a nuclear war. Washington's decision encourages nuclear weapons aggression which contravenes US obligations under the NPT. It also violates Article VI of the NPT that calls for cessation of the nuclear arms race and to promote nuclear disarmament. The development of RNEP would encourage the other P-5 countries and threshold nuclear states to abstain from observing any moratorium on nuclear weapons development. North Korea and Iran will pursue their nuclear weapons programme more vigorously. The result will be globally catastrophic.

RNEP calls for the "first-use" of nuclear weapons. Deploying RNEP for attacking bunkers suspected of hiding important military leaders is tantamount to usage of nuclear weapons against non-nuclear weapon states, which would also encourage the proliferation of nuclear weapons. The RNEP is still at a nascent stage of development and would require several tests to perfect it. Atomic testing by the US would provide the justification for other countries to resume atomic tests, leading to the proliferation of weapons of mass destruction and undermining efforts towards global disarmament.

The RNEP is therefore a dangerous, costly and an unjustifiable weapon. It undermines CTBT and several other treaties and encourages the proliferation of weapons of mass destruction. In the interests of global security, Washington should immediately halt its RNEP programme and reaffirm its commitment to the NPT.