That is one of the central debates Mr. Obama must resolve in the next few weeks, his aides say.

Many elements of the new strategy have already been completed, according to senior administration and military officials who have been involved in more than a half-dozen Situation Room debates about it, and outside strategists consulted by the White House.

As described by those officials, the new strategy commits the United States to developing no new nuclear weapons, including the nuclear bunker-busters advocated by the Bush administration. But Mr. Obama has already announced that he will spend billions of dollars more on updating America’s weapons laboratories to assure the reliability of what he intends to be a much smaller arsenal. Increased confidence in the reliability of American weapons, Vice President Joseph R. Biden Jr. said in a speech in February, would make elimination of “redundant” nuclear weapons possible.

“It will be clear in the document that there will be very dramatic reductions — in the thousands — as relates to the stockpile,” according to one senior administration official whom the White House authorized to discuss the issue this weekend. Much of that would come from the retirement of large numbers of weapons now kept in storage.

Other officials, not officially allowed to speak on the issue, say that in back-channel discussions with allies, the administration has also been quietly broaching the question of whether to withdraw American tactical nuclear weapons from Europe, where they provide more political reassurance than actual defense. Those weapons are now believed to be in Germany, Italy, Belgium, Turkey and the Netherlands.

At the same time, the new document will steer the United States toward more non-nuclear defenses. It relies more heavily on missile defense, much of it arrayed within striking distance of the Persian Gulf, focused on the emerging threat from Iran. Mr. Obama’s recently published Quadrennial Defense Review also includes support for a new class of non-nuclear weapons, called “Prompt Global Strike,” that could be fired from the United States and hit a target anywhere in less than an hour.