Washington — As Congress moves into the final rounds of dealing with the 1983 Pentagon budget, there is growing concern that the Reagan administration's plan for rearming America could in fact harm national security in the long run.
This paradoxical view is shared by many respected military experts outside the political fray - conservative as well as liberal - who question the shape as well as the size of Reagan's defense buildup.
In essence, they warn that the ''bow wave'' caused by massive procurement of major weapons systems will come in a few years, just as federal deficits peak, public support for stronger defense reaches the bottom of its traditional cycle, and pressure is greatest to cut.
What is likely to happen in this case, many warn, is the inevitable reduction of money earmarked for readiness, operations, and maintenance - the relatively unglamorous items lacking political clout that are the real backbone of a strong fighting and deterrent force.
What to do about this is a complex issue that necessarily involves key and often murky questions about force structure and the military dimension of foreign policy goals. But within this framework, many analysts agree that the pace of modernization (buying so many new expensive weapons systems, some of which still have questionable worth and serious technical problems) should be more evenly paced, if not slowed down. One of the more obvious targets here is Navy Secretary John Lehman's exuberant effort to expand US forces at sea to where they could threaten the Soviet Union anywhere through ''horizontal escalation'' of conflict.
Dr. Robert Foelber, a respected defense analyst with the relatively conservative Heritage Foundation, calls ''questionable'' the plan for two new aircraft carrier battle groups (costing at least $14 billion), the M-1 tank ($2. 7 million each), the divisional air defense gun ($6.1 million each), and the F- 18 fighter ($22.5 million each).
''These systems or force structures,'' he writes in a recent report, ''do not improve combat capability sufficiently in proportion to their high costs.''
Dr. Foelber notes that ''the administration has almost certainly underestimated the true cost of its weapons program by at least $100 billion.''
Philip Odeen, who has held senior posts in the Defense Department and National Security Council, warns that this ''bow wave of long-term procurement'' will inevitably lead ''to the pattern of cutting back on ammunition, spares, and things like that. . . . By putting too much money into procurement and investment, we're going to get ourselves into such a squeeze that we'll end up cutting readiness.''
While he favors higher defense spending, Foelber says ''the administration is making a serious mistake . . . in resisting a number of innovations in military strategy, tactics, and weapons hardware believed by many congressional and nongovernmental experts to be essential for fielding effective armed forces within realistic budgetary constraints.''
Other experts agree that reducing the number of M-1 tanks (for example) and buying more of the current M-60 tanks would result in savings beyond the initial price tag. They point to Congressional Budget Office studies showing that the M- 1 will cost 41 percent more to operate than the M-60.
William Kaufmann, an MIT economist who helped write Pentagon posture statements for Democratic and Republican administrations through the 1960s and ' 70s, says weapons buying could be cut by at least $130 billion over the next five years without harming military effectiveness. Cutting the rate of annual increase in the defense budget from 8 percent to 6 percent, he noted at a Brookings Institution seminar last week, would save about $250 billion over the same period and still provide a larger buildup than the Carter administration had envisioned.
Dr. Kaufmann's main target is the Pentagon's goal of a 600-ship navy. Holding to the present level of more than 500 ships could save some $77 billion in coming years, Kaufmann says. Others note that when allied naval forces and the size and quality of US ships are figured in, the Soviet Union is not as fearsome as the administration claims.
Kaufmann (now a consultant to the Brookings Institution) urges the US to ''stop playing hare to the Russian tortoise,'' and instead stick to a steady, more evenly paced buildup. To do this, he would reduce M-1 tank procurement by one-third (saving $4.5 billion through 1987), reduce procurement of Air Force F- 15 and F-16 fighters (save $3.9 billion), scrap the Navy's F-18 ($14.5 billion), cancel the two new nuclear aircraft carriers as well as several dozen other new ships, and cancel other programs including the Army's controversial AH-64 helicopter (a $6.4 billion program).
In the area of strategic nuclear forces, the MX missile (a program that will cost at least $26.4 billion) receives the most attention. The Aspen Study Group on the US Strategic Posture recently concluded that the United States should shift to a greater emphasis on sea-based strategic forces like the Trident II (D-5) missile, a weapon that will be very accurate and heavy but much less vulnerable than the MX.
''Most of our group felt we should delay the B-1, go ahead with the Stealth (bomber), and perhaps skip the B-1 since current aircraft with cruise missiles would be adequate through this decade,'' said Barry Blechman, vice-president of the Roosevelt Center for American Policy Studies and chairman of the Aspen group. Canceling the B-1 would save nearly $40 billion.
Congress as yet has not made much of a dent in the administration's unprecedented peacetime weapons-buying plan. It remains to be seen whether it can be convinced that trimming the list now in fact could result in a sturdier armed force.