The Congressional Budget Office said yesterday that the United States could end up spending anywhere from $111 billion to $140 billion between now and the year 2000 to build the nuclear blockbusters needed to destroy Soviet missiles buried under tons of concrete.
How much is spent, said the office's study paper prepared for Congress, will depend on how fast U.S. policy leaders moved into building "counterforce" weapons - those designed to knock out Soviet intercontinental ballistic missiles (ICBMs).
The MX missile that the U.S. Air Force has under development is considered a counterforce weapon because it would be accurate and powerful enough to crack Soviet concrete silos so that the missiles inside them could not be launched.
Backers of building counterforce weapons like the MX, which would be carted back and forth in an underground tunnel so it would be hard to hit, contend the weapon would persuade Soviet leaders that U.S. land missiles could not be destroyed in a surprise attack.
Opponents maintain that counterforce weapons like the MX would put a hair-trigger on nuclear war by impelling national leaders to launch their own missiles early in a crisis for fear the other side would destroy them. In the Carter administration's budget going to Congress late this month, the President will recommend a slower MX development program than the Air Force had in mind - earmarking $90 million rather than $250 million for the counterforce weapon, which could be deployed in the mid-1980s.
The Congressional Budget Office estimated that a go-slow approach for improving nuclear strategic weapons - those targeted on the Soviet Union - would cost $111.2 billion, partly because counterforce weapons like the MX would not be deployed.
A modest pace in deployment of counterforce weapons would cost $125.5 billion, the office estimated, while what it called the "prompt counterforce" option would cost $139.9 billion.
This most expensive option would include money for the MX and for a submarine-launched counterforce missile called the Trident II.
The office noted that cruise missiles might become accurate and powerful enough to knock out enemy missiles and thus qualify as counterforce weapons. But the weapon is not being deployed initially for this role.
The Pentagon, as part of its effort to assess the potential of the cruise missile, is running a series of test flights against stimulated Soviet defenses. The first such test was flown Saturday at Nellis Air Force Base in Las Vegas with a Navy Tomahawk cruise missile. The Pentagon said the test was successful, but would not detail in what respects.