The just-completed Clinton-Yeltsin summit included a handshake agreement on numerical reduction of nuclear weapons, though it was noticeably short on details. This could be a good sign, indeed, but PNS commentator William M. Arkin is troubled by the nearly unnoticed appearance of a new nuclear weapon -- the first since the end of the Cold War, and a weapon that could make the Russians feel more threatened than ever. Arkin is a columnist for The Bulletin of the Atomic Scientists.

The first new nuclear warhead to reach the Air Force since the end of the Cold War was formally received in February, and not one major newspaper or television network thought the event important enough to report it.

The weapon, called the "B61 Mod 11," is a 12-foot long nuclear bomb that can burrow some 50 feet into the ground before detonating with a blast many thousands of times greater than the largest conventional weapon in the U.S. arsenal. Nuclear war planners -- yes, they are still busy, despite President Clinton's constant assurances that the threat of nuclear war has disappeared -- claim the "earth penetrator" is needed to destroy Russian command bunkers buried deep underground.

The weapon previously earmarked for this task, the B53, is six million times bigger than the B61 Mod 11 in terms of its blast -- the arithmetic is truly stunning -- and so huge that the new B-2 stealth bomber can't easily carry it.

In the "logic" of nuclear war, the new weapon is necessary and an "improvement." In other words, smaller is somehow a moral step forward because fewer Russian citizens will be incinerated if the button is ever pushed.

Though President Clinton does not have to grapple with the nuclear nightmare as his predecessors did, the first order of business of his foreign policy team this year has been to coax Russian legislators into ratifying the START II Treaty. This agreement, signed in January 1993, would further reduce strategic nuclear arsenals to some 3,500 warheads.

Moscow has hesitated on this, complaining of the inequities and expenses involved in implementing the mandated reductions. One of the biggest problems is that economic and technological disarray in Russia means bombers are perpetually grounded, submarines hardly ever leave their ports and mobile missiles stay in their garrisons. The fact that Russia's nuclear arsenal is slowly disintegrating no doubt weighs heavily on the minds of Yeltsin's nuclear planners. In the "logic" of nuclear war, Russian nuclear forces are probably more vulnerable to an American first strike now than ever before.

However valid this scenario may be, it is in America's interest to alleviate these concerns. Yet despite our stated primary objective of improving relations with Russia, in actuality we are trying to pose a greater nuclear threat to Russian forces and command centers.

How did this happen? It starts when computer targeting models generated by Strategic Command in Omaha point to a few bunkers that might survive an all-out nuclear attack. The B53 is old and it is too big to fit into the B-2. A replacement is necessary.

In the bizarre world of nuclear deterrence, a few dozen B61 Mod 11 bombs will "improve" matters. The fact that we can still launch thousands of nuclear warheads to destroy everything else in sight is not enough.

Because the United States does not currently assemble new nuclear weapons from scratch, the B61 Mod 11 is a modification of a B61 bomb already in the arsenal. In fact, the Department of Energy downplays its significance, telling the trade newspaper Defense News it "is not new, in any way, shape or form." Surprisingly, many in the arms control community agree. Making too big of a deal about the "new" weapon, they say, might further upset START II ratification and even undermine the Comprehensive Test Ban Treaty.

In effect they are saying keep quiet about a new nuclear weapon so as to not get too many people upset. New or not new, the reality is that the B61 Mod 11 represents a mindset that does U.S. national security more harm than good. Russian naysayers can conclude rightly that their worst case view is indeed valid.

President Clinton authorized the B61 Mod 11 when he signed the 1994 Nuclear Weapons Stockpile Memorandum. The connection with larger U.S. interests was never made. START II ratification was not then considered critical. The otherwise minor program did not seem to signal either aggressive intentions towards Russia nor a potential for public outcry.

Now, as agreed reductions flounder and disarmament is utterly stagnant, nuclear advocates have their first post-Cold War weapon, with the aid of arms controllers who cannot see the forest for the trees.

It is the very routine nature of it all that is most frightening.