Official Washington loses an important balance wheel this month when Defense Secretary William J. Perry steps down. Perry heads back to Palo Alto leaving behind some large, unfinished tasks and some definite thoughts about what must be done to prevent a new era of superpow\er confrontation.

Perry's low-key, steadying presence helped bring order out of the bureaucratic tumult he inherited at the Pentagon in 1994. He became Bill Clinton's most important ambassador in Washington, trying to persuade senior military leaders to put aside their hostility to or skepticism about the youthful commander in chief who wriggled out of the draft in the Vietnam War.

That unenviable, behind-the-scenes ambassadorial role now falls to ex-senator William S. Cohen, the moderate Republican Clinton has designated to succeed Perry. Cohen, who never has run a large bureaucracy or served in the military, will have to earn his own acceptance from a Pentagon still suspicious of the man who appointed Cohen.

In a departure interview at his office this week, Perry characteristically avoided celebrating accomplishments. Instead he put heavy emphasis on the problems that lie ahead, especially with Russia and NATO expansion.

His stark description of Russian opposition to the expansion of the 16-member Atlantic alliance into Central Europe contrasts sharply with the rosier scenario painted by the White House, which routinely portrays Russian objections as temporary, easily surmountable obstacles.

Russian reaction to NATO expansion "ranges between being unhappy to being very unhappy," Perry said. "This is not just one or two or a few officials expressing a view, this is a very widely and very deeply held view in Russia. . . . It is going to take some years, I think, to get over that feeling. During those years, there have to be some events happening which help give them reasons for getting over it."

I asked the obvious: Like what? The first part of Perry's answer was also obvious. But he went on to lay out a surprising view of a future in which Russia could earn a limited share in NATO decision-making.

First, Perry urged those Russian officials who recognize that NATO represents no military threat to begin telling that to their public in a consistent, visible way. NATO in return should make "Shermanes\que" statements ruling out establishing bases or putting nuclear weapons in the new member states.

Those are familiar positions shared within the alliance. But what came next was neither.

Perry began by underlining the importance of a "NATO/Russia Charter" on European security. The United States would like the charter signed before the July NATO summit that will decide on extending invitations to new members. But the Russians, Perry pointed out, are refusing to sign before July because of concern "they will seem to be conceding NATO expansion."

The secretary believes the Russians will continue to refuse and will "take every action they can to try to dissuade NATO" from expanding. "So I see some hard times ahead of us between now and July."

After the summit the Russians will have to decide whether to continue their hard-line rejection or, as Perry hopes, accept a NATO-Russia Charter "that gives Russia a real voice in the security issues that NATO is acting on."

Does "real voice" imply that Russia will share in NATO decision-making, I asked. This is precisely what the Russians are asking for and what conservative critics of the administration say must not be granted. Perry, a scientist by vocation, answered with a simple, precise, "Yes," qualifying it only by adding that Russia would not be given a veto over NATO actions.

Perry illustrated his view of Russia gaining a say on NATO decisions by recalling that 15 months NATO ago was asked to keep peace in Bosnia:

"NATO met in its council, came to its decision, took its action and then invited Russia and other countries to join them. If the NATO/Russia Partnership Council had existed then under this NATO/Russia Charter, there would have been a council meeting at which Russia would participate in that discussion." NATO members would then have met and voted without Russia.

These are words on which to launch a grand strategic debate about the future of global stability.

The Perry proposition is at odds with other U.S. allies, led by Germany, who would guarantee a serious effort at reaching consensus with Russia in the joint council. A separate NATO vote would be taken only as a last resort. And while it is less than is demanded by the Russians -- they seek "co-decision" rights with NATO on European security -- Perry's proposal gives Moscow far more than many in the U.S. Senate will want to grant when they are asked to ratify NATO treaty revisions.

Perry's potentially controversial words are an effort to break the nasty logjam he sees forming in U.S.-Russian relations and to warn against the negative consequences likely to accompany a hasty program of NATO expansion.

Perry spoke so softly and precisely in administration debates that his presence was frequently overlooked. I fear that it is his absence -- or rather the absence of his steadying, intellectually honest contributions to policy -- that we will notice in the heated debates to come about the role of Bill Clinton's America in the world.