The New Strategic Arms Reduction Treaty (START) recently signed by the United States and Russia deals only with long-range nuclear weapons.

The treaty replaces the 1991 START I accord that expired last December.  It sets a limit of 1,550 deployed strategic - or long-range - nuclear warheads. Some of those are mounted on intercontinental ballistic missiles (ICBMs) fired from underground silos. Long-range warheads are also delivered from heavy bombers or submarines.

Experts say there is another class of nuclear weapons that needs to be addressed - weapons not covered by the New START Treaty.  Those are tactical - or short-range - nuclear weapons, including land and air-based missiles with a range of less than 500 kilometers - so-called "battlefield weapons."

Daryl Kimball, Executive Director of the Arms Control Association, a private research firm, says Russia has an overwhelming superiority over the United States when it comes to tactical nuclear weapons.

"There are various independent estimates that put the total number of Russian tactical nuclear weapons around 2,000 to 4,000," said Kimball.  "Now the reality is that only a few hundred of these are probably deployed in a manner that would allow for them to be used in a matter of days or weeks. The rest of them are in deep storage, are in various states of disrepair and are simply not available for use. The United States, on the other hand, has several hundred tactical warheads - a few of these, perhaps 200, are stored in Europe on five European NATO bases [Belgium, Holland, Germany, Italy and Turkey], theoretically for use in a conflict in Europe."

Many experts say the chances of a Russia / NATO war in Europe are virtually non-existant.

Frank Miller, a former senior official on the National Security Council under President George W. Bush, says there is no logical explanation for Russia to have such a large arsenal of tactical nuclear weapons.

"The Russians believe that their conventional forces have deteriorated to a point where they must rely on tactical nuclear weapons - mostly this is aimed at China," noted Miller.  "That's rather foolish.  For a country that suffered through the Chernobyl experience, the idea that they could, if deterrence failed against China and they had to use nuclear weapons, that they could use more than a handful of these weapons to signal to Beijing it has miscalculated, is mind-boggling. To have several thousands of these weapons is absolutely obscene."

Experts say the Russian tactical nuclear weapons pose a specific security risk that is not the case with long-range nuclear warheads.

"The strategic warheads are attached to very large pieces of metal: ICBMs, bombers, subs - you have some security risks, but very low theft risks there," said Joseph Cirincione, president of the Ploughshares Fund, a foundation focusing on nuclear weapons policy.  "The tactical weapons, however, are still scattered in some dozen different storage depots around Russia and they are much more vulnerable to theft - they are more mobile - these are still heavy objects, but something you could put in a large van or truck. So you're concerned that there might be some corruption or some penetration of your security around the tactical nuclear weapons by a force, say an Islamic fundamentalist force, a Chechen rebel force - so they do pose a greater risk of terrorist acquisition."

The issue of tactical nuclear weapons is not addressed by the New START Treaty. Critics of the accord say it should have been part of the START negotiations.

But many experts, including Daryl Kimball, say the New START Treaty had only one purpose, to reduce and put a ceiling on long-range nuclear forces. Tactical nuclear weapons were never intended to be part of the discussions.

"There has never been a U.S.-Russian arms control agreement that limits tactical nuclear weapons," added Kimball.  "The Reagan administration failed to accomplish this. The George Herbert Walker Bush administration failed to do this. The Clinton administration, the second Bush administration - so this is a tough problem. And I think it is extremely unrealistic to have expected the Obama administration, in less than one year after coming into office, to be able to conclude a further reduction of strategic warheads and for the first time in history, somehow manage to persuade the Russians to reduce tactical nuclear weapons."

Many analysts believe the next round of arms control negotiations between Washington and Moscow could include tactical nuclear weapons. But they say any new discussion will begin only after the New START treaty is ratified by the U.S. Senate and the Russian parliament. Experts say if that treaty is rejected, it would ruin any chances of further arms negotiations.