The Obama administration's preliminary agreement with Russia to reduce each nation's nuclear arsenal is a small step towards carrying out the president's pledge to seek a "world free of nuclear weapons." The question is, why was it so small?

According to an account in the New York Times, the goal of a new nuclear arms reduction agreement would be to reduce deployed nuclear warheads on each side to somewhere between 1,500 and 1,675. Delivery vehicles -- the ballistic missiles and bombers that can be used to drop the bomb -- would go down to somewhere between 500 and 1,000. This would represent a cut of one-quarter to one-third from current levels. But it would not address the thousands of nuclear warheads that are being held in reserve -- not deployed, but capable of being deployed upon demand.

What do these numbers mean? First, if these numbers make it into a final agreement, both the United States and Russia will still maintain massive nuclear overkill. But if a formal agreement -- a treaty -- is concluded, it would be the first such accord to be reached since the admininstration of George Bush the elder in the early 1990s. That in itself would represent progress, especially since a treaty would maintain procedures that would allow each side to verify that the other was making promised reductions -- procedures that would be the cornerstone of any agreement seeking additional cuts.

I would have liked to see much deeper reductions -- to perhaps 500 to 1,000 warheads on each side, including those being held in "reserve" -- as a first step towards eliminating these devastating weapons altogether. No doubt the Obama administration's more limited approach has been tempered by concerns about what kind of treaty could make it through Congress with a two-thirds majority, which would mean bringing along at least a half dozen Republicans. But I would have liked to see that fight -- a popular president saying we don't need thousands of nuclear bombs any more versus a few members of the Senate arguing that we should maintain them at unconscionably high levels.

Supporters of disarmament have a two-fold task going forward: to back up the Obama administration against attacks from the right, which have already begun; and to make the case for further reductions, either now or in a second round of talks that should commence later in President Obama's first term.