The Clinton administration has quietly changed US nuclear weapons policy to permit for the first time attacking Iraq with tactical atomic warheads, according to US officials.
The top-secret directive, signed by President Clinton in November, is part of the administration's contingency plan to consider using atomic bombs on Iraqi weapon sites if President Saddam Hussein initiates a major biological attack on Israel or other neighbouring countries, according to White House and Pentagon officials.
Administration officials said the policy shift involving tactical nuclear weapons and so-called "rogue states", such as Iraq, was made as part of the most extensive overhaul of US policy regarding both strategic and tactical nuclear weapons since the Reagan administration.
"It is US policy to target nuclear weapons if there is the use of weapons of mass destruction" by Iraq, said a senior Clinton adviser who spoke on condition of anonymity. "Whether we would use it is a another matter."
The new policy was part of Presidential Policy Directive 60, which Clinton approved after consultation with the Defence Secretary, Mr William Cohen, and Gen Hugh Shelton, chairman of the Joint Chiefs of Staff.
The United States is the only country to have used atomic weapons in war, dropping bombs on the Japanese cities Hiroshima and Nagasaki in 1945. Through the Reagan administration, US policy promised massive retaliation to prevent nuclear confrontations with the Soviet Union and China.
With the end of the Cold War, the threats changed from longrange strategic nuclear weapons aimed at major nations to new, more flexible weapons of mass destruction that could be used by smaller rogue states such as Iraq.
Administration officials said they feared the Iraqi president might use a handful of Scud rockets to spread a powdered version of anthrax spores over Saudi Arabia, Kuwait and Israel, killing thousands and making parts of Riyadh, Kuwait City and Tel Aviv uninhabitable for decades.
During the Persian Gulf war in 1991, President Bush threatened to retaliate with nuclear force if President Saddam Hussein used biological weapons, but his administration never formally adopted a policy, officials said. But it was Mr Bush's warning that has evolved into Mr Clinton's directive.
Until November, first use of nuclear weapons on Iraq would have violated US pledges never to make such an attack on a signer of the nuclear Non Proliferation Treaty, which includes Iraq. But US officials say President Saddam's efforts to develop nuclear weapons would forfeit Iraq's treaty protection. Mr Clinton's threat has been deliberately vague. A Pentagon spokesman, Mr Ken Bacon, said last week the United States refused to "rule in or rule out" the use of tactical nuclear warheads. Mr Bacon's words have caused rumblings abroad and among the arms control community.
"It's a mistake to threaten Hussein with nuclear weapons because it will not deter him," said Mr William Arkin of the Bulletin of Atomic Scientists. Most senior military planners now prefer conventional weapons for the massive strike being considered if Iraq refuses to allow UN weapons inspections. But in the latest showdown, the administration wants President Saddam to include in his current calculations the possibility of one or more B61 nuclear warheads finding their way to Iraqi targets.
The B61 series of tactical warheads involved in the contingency planning are so-called "mininukes" with an explosive force less than 1 kiloton. The bomb dropped on Hiroshima had an estimated 13 kilotons of explosive power. Even so, the mini-nukes are 300 to 500 times more powerful than the largest conventional, non-nuclear warhead in the US arsenal.
Some US intelligence officials suspect that the remnants of President Saddam's chemical and biological weapons are hidden in European-built bunkers made of reinforced concrete.
During the Persian Gulf war, these bunkers were attacked with limited success by 2,000 lb television-guided bombs dropped with pinpoint accuracy on laser-designated targets. This was one reason the air force pushed its effort to develop a 5,000 lb bomb, the GBU28, which could cut through 11 feet of reinforced concrete.
Since then, the air force has modernised the GBU28 and produced hundreds of the laser-guided bombs with conventional warheads. They can be dropped by F15E fighter-bombers or the B-1, a subsonic strategic bomber now poised in Bahrain.
The mini-nuke available for the bunker attack most likely would be the B61-7, a bomb dropped from a fighter-bomber by parachute to explode at the surface. Its explosive force ranges from 300 tons to 500 tons of high explosive.