Four months into his administration, President Reagan appears determined to follow through on his campaign rhetoric of confrontation and test of strength with the Soviet Union in what foreign affairs experts see as a sharp departure from the recent history of U.S. politics.

In the view of these experts, the Reagan administration is trying to sustain what it championed in winning office -- a global ideological and political counteroffensive against Moscow with an emphasis on arms buildup to make credible its political efforts. They see such a course as significantly altering the tone and substance of Soviet-American relations in the 1980s.

In the long run, this course increases risks of nuclear confrontation, according to experts, some of them with long years of experience in dealing both with the Soviets and with U.S. policy formation. In the short run, they say it could have an adverse impact on the U.S. economy and on America's relations with its closest allies.

Almost without exception, they see it as a policy apparently unsupported by a carefully calculated strategy.

"They [the new administration] have no foreign policy at all," said Malcolm Toon, former U.S. ambassador in Moscow. "They ought to start thinking about what sort of relationship we should have with Moscow. Frankly, I don't see any evidence of this."

Reagan administration spokesman say that a comprehensive program for dealing with Moscow is now being put together, although there is as yet no consensus among various elements in the administration on when the lines of communications with Moscow should be reopened.

High officials say the Reagan administration would build a "special" relationship with the Soviet Union around efforts to control nuclear weapons. The strategy now being developed would be a departure from the policies of containment as well as from detente that have dominated U.S. policy toward Moscow since World War II, according to these officials, who refused to elaborate.

A leading administration official described the current U.S. posture as follows:

"We have got to strip confusion out of our dealing with the Soviet Union . . . that means a period of stiff rhetoric -- line drawing if you will. . . . First and foremost there has to be a clear understanding of where the president stands. We cannot condone the right of the Soviet Union to affect historical change by bloodshed and terrorism."

In the absence of a clearly defined strategy, the administration's operating policies are shaped around Reagan's campaign pledge to restore America's military superiority over the Soviet Union. But the danger that the arms buildup may itself overwhelm the strategic objectives of the United States is generating apprehension inside the government as well as outside.

A series of interviews with foreign affairs specialists and businessmen in recent days revealed concern about the likely impact of Reagan's defense budget on future arms control efforts as well as about the ability of the American economy to sustain such massive expenditures.

Most of those interviewed are not Reagan supporters. But their misgivings, nevertheless, are not summarily dismissed by everyone inside the administration. A few insiders even share them, as do many specialists in universities and the private sector.

The central element of Soviet-American relations is a shared interest in avoiding "an all-out nuclear war," Toon said. "I hope that this is still the case. And the essential part of this is the SALT [strategic arms limitation talks] process. We have to find a way to reinstitute this process."

In Toon's view, the United States had to move quickly to reverse "a trend toward military weakness." But, he said, the absence of U.S. strategy should not be obscured by "intermperate" statements about the Soviet Union made by top American officials or by an "overreaction" to reports of Cuban and Soviet intervention in El Salvador.

Zbigniew Brzezinski, former president Jimmy Carter's national security adviser who is currently at the Center for Strategic and International Studies, echoed this view.

"I applaud many of the things that are happening," he said. "But you cannot substitute tougher talk and increased spending for defense" for an overall strategy.

The prospect of a nuclear arms race includes some inherent dangers, especially since both sides are contemplating entirely new types of weapons. Some experts contend that both sides would spend vast amounts of money with neither gaining a decisive advantage.

It has been argued that all presidents eventually become champions of arms control because of the awesome personal responsibility involved in their control of the "nuclear button." Moreover, arms control is strictly a presidential issue. Given the fact that any arms control effort can be seen as either securing peace or demonstrating weakness, presidential leadership is essential to rally public opinion behind it.

So far, foreign policy analysts say, there has been no change in Reagan's attitude. They see deep divisions within the administration over arms control. Without a clear position in this issue, there is no policy toward Moscow.

On the economic side, the projected increases in defense expenditures would produce a "greater chaos" in the U.S. economy, according to Nobel Prize-winning economist Wassily Leontief. He predicted higher inflation, soaring interest rates, a drain on productive investments and eventually more unemployment.

But Seweryn Bailer of Columbia Univesity said increased arms expenditures would put a greater strain on the Soviet economy and that the new trend in military balance would create "much higher risks" on possible future Soviet adventures. Bailer is one of the country's leading experts on internal Soviet politics.

A secondary aspect of this policy is the expected negative impact on East-West trade. Donald Green of Chase Manhattan said his bank is now discouraging its clients from undertaking projects in the Soviet Union "because of the unpredictability of U.S. political climate."

Executives of corporations involved in East-West trade privately expressed concern about plans to restrict exports to the Soviet Union on grounds that they involve transfers of technology. A senior corporate executive, who actively support Reagan's campaign, said that the problem of corporate America is that it had few ties with the new president.

"All those businessmen around him are California guys who made money in real estate, drug store chains or playing the market," said the executive who asked not to be identified. "Major corporations do not have an in with the new crowd."

Some experts such as Harvard political scientist Michael Mandelbaum predicted that the administration would discover the weaknesses of a one-track approach to policy by next year when it would be forced to seek "compromise between strategic common sense and political commitments made during the campaign."

Yet, even the most optimistic projections of the administration's course, including an ultimate resumption of arms control efforts, also indicate that the arsenals of the two superpowers will inevitably increase during the current decade, with rebounding consequences.

Most experts say that despite public statements about the importance of strategic arms limitation, there seems to be little interest in Washington at this time in reviving the SALT process or even resuming a "businesslike" relationship with Moscow.

"We've got to begin the dialogue with the Soviets," Toon said. "The only thing we have done so far is lift the grain embargo and that was a big mistake because it sent a wrong signal to Moscow and to our allies as well."

But other critics such as Raymond Garthoff of Brookings Institution contend that the administration is "pushing" the Soviet Union into a new arms race.

"We are now pushing the Soviets into moving up in their strategic programs just at the time these were about to level off," Garthoff said. "We have prematurely reached the conclusion that they were going to go up indefinitely rather than they were going to round up their programs and not necessarily go into new generations of weapons."

Garthoff, who served as ambassador to Bulgaria and was one of the key arms control experts in the Nixon administration, argues that Moscow is much more serious about nuclear arms limitation than Washington admits. This view is shared by important segments of West European public opinion as well as by many left-leaning politicians in NATO countries.

In a recent article in the magazine Foreign Policy, Garthoff outlined in detail his claim that the Kremlin's assertions about the decline in the number of their intermediate-range rockets and bombers oriented toward Western Europe "are valid." U.S. defense spokesmen, however, continue to insist that the Soviets "continue to modernize and enlarge their already formidable" nuclear forces in the European theater.

Other experts disagree with Garthoff. Toon said that "we've got to get on with the job of TNF [theater nuclear force reduction negotiations] and make the Russians pay a reasonable price to stay equal with us." But, Toon said, the administration "has got to articulate a strategy" toward the Soviet Union and "start a dialogue" toward a resumption of the SALT process, possibly using the TNF issue to do so.

Critics of the Reagan administration as well as many of America's allies are now viewing Washington's attitude toward the TNF negoitations as the litmus test of U.S. political intentions about arms control.

The break in the SALT process comes at a crucial juncture because the United States is seen as still enjoying a substantial technological advantage, particularly in the area of cruise missiles and the development of the space shuttle. In some ways, this is similar to the U.S. advantage in 1970 -- it had developed MIRVs, or multiple, independently targeted, reentry vehicles. It meant that one U.S. rocket carried several warheads. The Soviets developed the same technology five years later, the fact that in large part is the source of current perception of vulnerability of the U.S. land-based strategic force.

Some experts argue that if and when the Soviets develop the cruise missile system, "we may go beyond the point of verification," as one put it. Cruise is a relatively inexpensive and highly effective low-flying rocket that can be mass-produced. It has a special guidance system that allows it to follow the contours of the ground to avoid early detection.

But there is also the question of the social and economic burden massive arms expenditures may impose on the United States. In his recently published book "The Nuclear Revolution," Mandelbaum argues that in the first three decades after Hiroshima, "the choice between guns and butter was not particularly painful.The United States has been able to afford both. Guns, at least nuclear guns, have been relatively cheap.

"In the 1980s this is likely to change. The cost of nuclear weapons will rise sharply as the hardware built in the 1950s and 1960s is replaced. When it was built, the U.S. economy was growing rapidly. In the 1980s it is likely to be growing at a snail's pace or perhaps not growing at all. And as the economic pie is shrinking, or failing to grow, more people will be demanding larger shares of it."