President Clinton last month issued new guidelines for the targeting of U.S. nuclear weapons, jettisoning a Cold War dictum that the military must be prepared to win a protracted nuclear war that would devastate the globe, according to senior administration officials.

Clinton's new orders to the Secretary of Defense and chairman of the Joint Chiefs of Staff require instead that the military aim its nuclear forces to deter the use of nuclear arms against U.S. forces or allies simply by threatening a devastating response, and drop any planning for a long nuclear war, the officials said.

Clinton's highly classified directive replaces one signed by President Ronald Reagan in 1981 and marks the first time since the end of the Cold War that nuclear targeting guidance issued at the presidential level formally recognizes that no nation would emerge as the victor in a major nuclear exchange, the officials said.

But the directive nonetheless calls for U.S. war planners to retain long-standing options for nuclear strikes against the military and civilian leadership and nuclear forces in Russia. Such planning reflects a widespread view among military officials in both nations that each side still poses a potential nuclear threat to the other -- even though Washington has proposed to give Moscow $242 million in foreign aid next year.

Several sources said the directive's language further allows targeters to broaden the list of sites that might be struck in the unlikely event of a nuclear exchange with China. In addition, the sources said, the directive contains language that would permit U.S. nuclear strikes after enemy attacks using chemical or biological weapons, an idea that has been hotly debated by independent arms control experts.

Clinton's action marks the first formal adjustment in 16 years of presidential policy for the targeting of U.S. nuclear weapons and could pave the way for further reductions in the total number of such weapons by requiring that fewer be held in reserve for a protracted war, several senior officials said.

But they added that the directive reflects more continuity than change in the military's effort to ensure that its strategic nuclear arms are ready to use at a moment's notice, an effort that costs an estimated $33 billion annually.

The document affirms, for example, that the United States will continue to rely on nuclear arms as a cornerstone of its national security for the "indefinite future," and that it will retain a triad of nuclear forces consisting of bombers, land-based missiles and submarine-based missiles, according to Robert G. Bell, a special assistant to the president and senior director for defense policy at the National Security Council.

Independent critics of U.S. nuclear policy have suggested that Washington consider following the example of France, which gave up its vulnerable force of land-based strategic missiles, partly to save money and partly to undercut incentives for an enemy first-strike against such missiles. Both France and England rely solely on nuclear-equipped bombers and submarine weapons for deterrence.

Several sources said the presidential decision directive, known informally as a PDD, was prepared within an extraordinarily restricted circle of senior policymakers -- numbering no more than two dozen people -- from the National Security Council, the Defense Department, the Joint Chiefs of Staff, the CIA, and the State Department, as well as the office of Vice President Gore.

The document sets only broad targeting policy and will be translated over the next 10 months into more concrete military requirements -- such as preparations to strike specific targets -- by the military staff of the Strategic Command (STRATCOM), headquartered in Omaha, the officials said.

They said the directive was principally drafted by the acting assistant secretary of defense for international security, Franklin Miller, a career official who has worked on nuclear weapons issues at the Pentagon since 1981. In preparing the document, policymakers did not consult officials at the Department of Energy -- which designs and produces nuclear arms -- and the Arms Control and Disarmament Agency, including ACDA's director, John D. Holum, whom Clinton has nominated to become undersecretary of state for arms control and international security matters.

Bell declined in an interview Friday to specify the length of the directive, the date it was signed or its formal title; he also declined to answer questions about the countries it names as targets of U.S. nuclear arms. He said that the secretive deliberations were warranted by their extreme sensitivity and that the administration had not planned to make a public statement about the directive or discuss it with foreign governments. He said the White House agreed to comment only because The Washington Post was preparing an article on the directive.

"The presidential directive describes in general fashion the purposes U.S. nuclear weapons serve and provides broad guidance for military planners who prepare the actual operations plans and targeting plans for our nuclear forces," Bell said. It "recognizes that {because} we're at the end of the Cold War" and many changes have occurred in Russia and elsewhere over the past seven years, "nuclear weapons now play a smaller role in our nuclear security strategy than at any point during the nuclear era."

Bell, who was reading from notes, said that "most notably the PDD removes from presidential guidance all previous references to being able to wage a nuclear war successfully or to prevail in a nuclear war. . . . The emphasis in this PDD is therefore on deterring nuclear wars or the use of nuclear weapons at any level, not fighting {with} them."

At the same time, Bell added, "it would be a mistake to think that nuclear weapons no longer matter, or that they no longer matter to this administration." Such weapons are still needed to deter "aggression and coercion" by threatening a response that "would be certain and overwhelming and devastating." He noted that the directive still allows the United States to launch its weapons after receiving warning of attack -- but before incoming warheads detonate -- and also to be the first to employ nuclear arms in a conflict.

The directive was prepared in part at the urging of then-Joint Chiefs of Staff Chairman Gen. John Shalikashvili and Gen. Eugene Habiger, the STRATCOM commander, who told Clinton last February that the requirements of Reagan's directive could not be met if the U.S. arsenal was reduced much below the ceiling of 3,000 to 3,500 weapons set by the 1993 START II treaty with Russia. When Clinton and Russian President Boris Yeltsin agreed the following month eventually to seek a new, lower ceiling of 2,000 to 2,500 weapons, the new guidance already was being drafted, Bell and other officials said.

The policy shift that Bell highlighted involves one of the most controversial features of Reagan's 1981 directive, which the Pentagon summarized in a 1982 classified document as requiring that U.S. nuclear forces "must prevail even under the condition of a prolonged war."

Many critics alleged then that preparing to fight such a war was ludicrous, given the certain destruction of U.S. and Soviet societies in a modest nuclear exchange; they also predicted that the military would squander huge sums trying to develop weaponry and communications systems purportedly capable of outlasting such an exchange.

Partly to quiet the controversy, Reagan signed a joint statement with Soviet President Mikhail Gorbachev at a 1985 summit meeting pledging that "a nuclear war cannot be won and must never be fought." But Bell said that until now, U.S. targeting policy did not reflect this rhetoric, because neither Reagan nor President George Bush had sought to amend the secret presidential directive.

Another senior administration official, who spoke on condition he not be named, said this policy shift is "significant" because it will enable the Pentagon to trim the number of nuclear weapons held in reserve for possible use after an initial nuclear exchange or two -- a force estimated at more than 1,000 warheads, out of the roughly 8,000 nuclear weapons now deployed on U.S. bomber aircraft and intercontinental-range ballistic missiles.

But Leon Sloss, a former Pentagon official who was the principal drafter of Reagan's directive, said that in his view, "removing the idea of prevailing {in a nuclear war} . . . does not change the substance very much" because winning "would have been nice, but it was never very realistic" and the ambition did not greatly affect what the Pentagon did. "We were not in a position to prevail, even when we had 10,000 {deployed} nuclear weapons," Sloss said.

William Arkin, a nuclear expert who consults for various arms control groups, similarly called Clinton's policy shift superficial. "In theory, this could free up a lot of resources and brain power that go into preparing to fight World War IV. But as long as we remain wedded to the option of taking out all of their strategic forces and nuclear command systems with a hair-trigger attack posture, then we really haven't adjusted to the post-Cold War period," he said.

Bell said the new directive did not alter a previous requirement that target planners must be prepared in a crisis to offer the president various nuclear attack options, from initiating a major strike involving thousands of warheads to limited attacks involving a much smaller number of arms.

Since the late 1970s, for example, the military has had a special targeting plan for China that required U.S. weapons to be held in reserve for possible strikes against Beijing's handful of strategic warheads, its leadership, its petroleum supply and its electrical power system. The aim of the plan was to ensure that China could not become the world's most powerful nation following a general nuclear war between Russia and the United States.

Bell declined, however, to address a reported shift that would allow the military to plan attacks against a wider spectrum of targets in China, including the country's growing military-industrial complex and its improved conventional forces. Another official said there was "no debate with respect to the targeting of China," even though Clinton last month said he told Chinese President Jiang Zemin that he wanted to "establish cooperation, not conflict, as the model for U.S.-China relations in the 21st century."

According to a written statement to Congress in June by CIA Director George J. Tenet, "China is presently modernizing both the size and the quality of its strategic missile force. The qualitative modernization effort may be benefiting from Russian technology and expertise. Currently, a small number of China's strategic missiles have sufficient range to target large urban areas in the United States." The directive also demands general planning for potential nuclear strikes against other nations that have what Bell called "prospective access" to nuclear weapons and that are now or may eventually become hostile to the United States. A separate official described these countries as "rogue states" specifically listed in the directive as possible targets in the event of regional conflicts or crises.

The idea of targeting non-nuclear states with U.S. nuclear weapons or planning for U.S. nuclear strikes in retaliation for poison gas and germ weapons attacks has become increasingly controversial since 1995. At that time, the United States and the four other major nuclear powers -- Britain, China, Russia and France -- formally pledged not to use nuclear arms or threaten their use against countries that are not trying to develop or acquire nuclear arms.

Bell said Clinton's nuclear targeting directive reflects "much greater sensitivity to the threats" posed by chemical and biological attacks since the previous directive was issued. But he added that it only reiterates what senior administration officials already have said about the issue during the past year -- namely, that if any nation uses weapons of mass destruction against the United States, it may "forfeit" its protection from U.S. nuclear attack under the 1995 pledge.