A few days before Congress adjourned, Sen. Joseph R. Biden Jr. (D-Del.) dared to suggest publicly that the Soviets soon will have more to fear from our nuclear weapons than we now fear from theirs.

While that might sound like good news, it is bad news if one accepts the popular wisdom of the nuclear age that the best way to keep the United States and the Soviet Union from blowing each other up, along with much of the world, is to make pushing the button first look suicidal.

But new nuclear weapons both sides are building challenge that wisdom as never before.

Missiles are becoming so accurate and powerful that there may be no way to keep land missiles from being destroyed in a surprise attack.

This increases the temptation to fire at the first warning of attack rather than risk having missiles caught in their silos.

War planners in both Washington and Moscow must deal with the growing arsenal of first-strike weapons threatening their countries.

The Soviets already have their SS18 and SS19 silo busters on the line and are working on a better one. The United States plans to have two new silo busters deployed before the decade is out: the MX land missile in 1986 and the D5 Trident II submarine missile in 1989.

Biden is one of the few senators who has stepped back far enough from the debate over how the MX should be based to warn of the possible long-range consequences of deploying such weapons. He told Defense Secretary Caspar W. Weinberger at the Senate Foreign Relations Committee hearing last week:

"The Soviet Union has to assume the worst, since in fact we were the only nation to ever drop a nuclear weapon; since in fact we have been the only ones who ever demonstrated the willingness to do that. I believe we never will, but it is prudent for them to plan for it . . . .

"With the MX missile, and with the D5, we will be in a position, if we were to choose, which we are not going to choose, to inflict serious damage, overwhelming damage upon the Soviet Union if we struck first -- a first-strike capability that far exceeds what the Soviets' first-strike capability is now. Everything that I have been told leads to that conclusion.

"If that is true, I do not know how we can reach an arms control agreement with the Soviet Union if neither of those items are negotiable."

Weinberger replied, "I am not really going to get into any kind of hypothetical speculation about the United States making a first strike or what would happen if we did, because it is totally opposed to our policy. Our policy is to deter a first strike." He added that President Reagan's arms control proposal "provides for substantially, vastly lower levels than now exist on both sides."

The SS18, SS19, MX and D5 are all designed to carry several nuclear warheads into space and launch each one at a precise point along the flight path. Once dropped off the missile "bus," the warhead is supposed to glide like a paper airplane to its target and explode over the missile silo or on the ground near it. Sending two warheads to one missile silo, thus bracketing it with thousands of tons of explosive power, virtually assures destruction of present-day silos.

The Pentagon claims the Soviets already have so many silo-busting missiles that their warheads could bracket the existing U.S. force of 1,000 Minuteman and 51 Titan intercontinental ballistic missiles, destroying 90 percent of them. It would take less than half of the Soviets' land missile force to do this, according to the Pentagon.

The United States is responding to this threat both defensively and offensively. It is searching for better ways to base land missiles to ensure they could survive a surprise attack by even this new generation of warheads. It is building the MX and D5 hard target killers to threaten the Soviets in kind.

Although Weinberger stresses that the United States has no intention of launching a first strike against the Soviet Union with these new missiles, war planners the world over focus on capabilities, not proclaimed intentions. And there no longer is any secret about the first-strike capabilities of the Soviet and American blockbusters already deployed or on the way.

In contrast to the secrecy wraps the Air Force tried to put on first-strike capabilities of missiles in the past, former Air Force chief of staff Lew Allen Jr. has said that "it is a fact that the MX program will have some first-strike capability."

Air Force Brig. Gen. J.P. McCarthy, in briefing the House Appropriations subcommittee on defense on the MX "Dense Pack" deployment scheme, said that with that new weapon "we put Soviet hard targets at risk, which is the principal reason why we need the MX missile."

As for the D5 missile destined to go inside Trident submarines, it, too, will have first-strike potential, at least in the eyes of Soviet worst case planners, because its warheads will be accurate and powerful enough to blow up silos or underground command centers. Rep. Thomas J. Downey (D-N.Y.) calls the D5 "the ultimate first-strike weapon" because the submarine could fire it at such a low trajectory that Soviet warning radars could not see it coming.

Edward Rowny, chief U.S. negotiator at the strategic arms reduction talks (START) in Geneva, told The Washington Post that "we want the Soviets to worry about our counterforce capabilities in the 1990s the way we have been worrying about theirs in the 1980s." A counterforce weapon is one that can destroy missile silos or other protected military forces.

Rowny reasoned that such mutual counterforce threats would help, rather than hinder, arms control negotiations, while critics contend that such a gun-to-the-temple approach threatens to destabilize the balance of terror between the two superpowers.

Forty House members are so alarmed about the dangers of the United States and the Soviet Union menacing each other with first-strike weapons that they have introduced a resolution in an attempt to force the Congress to look before it leaps any farther down this path.

The resolution, to be reintroduced next year, calls for Congress to resolve that as part of the START talks the United States and the Soviet Union "should place the highest priority on efforts to reduce and eliminate the fear by either nation of a nuclear first strike against it by the other, and should seek a verifiable agreement that produces stability in the strategic relationship between the two nations by ensuring that a nuclear first strike would not confer upon the attacking nation even a hypothetical advantage."

Rep. Albert Gore Jr. (D-Tenn.), son of the senator who took a leading role in arms control efforts in the 1960s; Rep. Les Aspin (D-Wis.), a member of the House Armed Services Committee, and Downey, a former delegate to the arms control talks, are at the forefront of sponsors trying to make the resolution a vehicle for assessing the long-term consequences of deploying first-strike weapons.

They contend that it is no longer the number of weapons that threatens to upset the balance of terror, but the type of weaponry. START, they warn, would allow each side to deploy so many silo busters that neither nation's land missiles would be safe from being bracketed by nuclear warheads.

A recent Library of Congress analysis buttresses this view by concluding that, under START, both the United States and the Soviet Union would be able to gang up on each other's land-based missiles with multiple, independently targetable reentry vehicles, known as MIRVs. Rowny confirmed that this could happen under START, adding that it underscores the need to find a way to make land missiles more survivable.

Gore said in an interview that the long, vain struggle to find an impregnable home for the MX should serve notice that "the only way to make it survivable is through arms control."

He said that even if the United States and the Soviet Union deployed the same number of silo-busting missiles, there would not be a stable balance of terror. Each side would still worry about losing its missiles to the other, he said, and "this would be an instable balance."

By pushing for deployment of large numbers of the MX and D5 missiles, Gore contended, the Reagan administration is trying to open up "an intimidation gap" on the Soviets. "The window of vulnerability is really vulnerability to political intimidation," he said. "The intimidation stems from the fear that one side might carry out a successful first strike."

Aspin said he believes the prime objective of arms control should be "to reduce the probability of war breaking out." Under this definition, he said, the United States and the Soviet Union would be less likely to start a nuclear war if each knew the other had so many weapons that not enough of them could be knocked out in a first strike to make it worthwhile; the retaliatory wave would be too great.

Even if both sides should agree to deploy a smaller number of first-strike weapons, Aspin reasoned, "we've got an unstable situation because the guy who fires first has the advantage."

He said he has been voting to develop the MX and D5 hard target killers because he did not want to give the Soviets a free ride and "I wanted to force the issue up" at the talks in Geneva.

Asked why Weinberger has not endorsed the first-strike resolution, Downey said, "The people around him are patently hostile to arms control." Downey added his opinion that, on the basis of congressional questioning, Weinberger does not understand the geo-political implications of strategic weapons such as the MX and the D5. Downey said it is simplistic of Weinberger and others in the administration to keep saying that the president wants to reduce the number of weapons on each side without at the same time appreciating that "it is the types of weapons that are important, not the number of weapons."

The effort to gain control of silo-busting weapons is reminiscent of the unsuccessful effort in 1969 of then-senator Edward W. Brooke Jr. (R-Mass.) to persuade President Nixon to halt development of MIRV warheads, which now confront the United States and the Soviet Union with first-strike threats. Lamented former secretary of state Henry A. Kissinger in looking back in 1974 on the administration's decision to go full speed ahead with MIRV: "I wish I had thought through the implications of a MIRVed world."