Proposed new advances in U.S. strategic and tactical nuclear missiles could lead the Soviet Union to start another round in the arms race, according to the Carter administration's fiscal 1980 arms control impact statements, which were released yesterday.

In a blunt section on U.S. plans to develop a medium-range missile that could hit Soviet territory from Western Europe, the statement notes that if NATO deploys "a sizable number of cruise missiles... the Soviets would be faced with a new type of NATO force which to them represented an incremental strategic threat."

The response to such a weapon, the statement said, "could lead to further increases in Soviet weapon programs and political tensions...."

The statement allows for the alternative conclusion that such new NATO missiles could serve "to stengthen deterrence" and to increase the West's bargaining leverage in arms control negotiations.

The document asserts that a new land-based MX ICBM and a submarine-launched Trident II missile, could by 1990 threaten first-strike destruction of Soviet fixed ICBM silos.

"This could have destabilizing effects and thus a potential negative arms control impact," the statements said.

One step the Soviets might take is to adopt a policy called "launch under attack," according to the statements. This would have the Soviets fire their missiles if they thought the United States had launched an attack against them.

Another Soviet response might be to deploy more strategic missile-firing submarines or turn to land mobile ICBMs.

Like the United States, the Soviets also could go to a basing system of multiple shelters for a single missile that "would make more difficult the assessment of Soviet capabilities and the negotiation and verification of arms control agreements," the document says.

The "less likely" course that would follow the increase in Soviet ICBM vulnerability, according to the statements, would be an "increase [in] their incentives to negotiate further mutual reductions in the number of ICBM launchers."

The statement focuses particular attention on the big proposed MX ICBM that the Carter administration has put into development.

The MX as now planned would have 10 warheads on each missile and each one would be capable of knocking out a Soviet missile silo. The present Minuteman III, which the MX would replace has only three warheads and less power and accuracy.

The document says that deployment of the MX would raise "complicated and contentious" arms control issues.

Those issues are currently being debated within the Carter administration as the April 1 date approaches by which time the Defense Department is supposed to decide how the MX is to be based.

One side is arguing that the threat posed by MX will push the Soviets to seek a wide-ranging SALT III (strategic arms limitation treaty) agreement.

The other side within the government is countering that because most of the Soviet strategic deterrent is in land-based systems threatened by MX, deploying the missile might prompt "an increase in the number or change in the character of Soviet weapon system programs."

The deployment decision on MX -- no matter what its basing mode -- will not be made until 1983, according to the statements. Thus, the administration document says, a decision on the arms control issues can be deferred "pending... exploration [with the Soviets] of mutual limitations on such systems."

The discussion of the medium-range missile in the arms control impact statements, was designed to raise problems not previously discussed in public, according to those involved in writing that section.

Soviet concern over the prospect of a NATO-based missile that could reach Russian territory was injected into the current strategic arms limitation talks although the weapon, itself, is considered tactical by the United States.

To satisfy the Russians, the United States agreed to put in the three-year SALT protocol a range limitation of 360 miles on any deployed land-based cruise missile. Meanwhile it could develop one with a much greater range.

That language raised concern among the NATO allies and some SALT critics that the United States had limited itself while not inhibiting Soviet deployment of its new mediumrange missile, the SS20.

Yesterday's statement makes clear that the United States understands the Soviet concern.

A cruise missile, or some extended-range version of the current 400-mile Pershing missile, or a new medium range missile "would significantly add to the capabilities of U.S. and NATO theater nuclear forces to put Soviet territory at risk," the document says.And, although the Soviets themselves have a large number of medium-range systems that can cover European targets, none can hit the United States.

Thus deployment of the missiles could cause Soviet leaders to see themselves facing a new U.S. arsenal capable of striking the USSR" that is not included in any strategic arms agreement. Basing such weapons in West Germany, the statements add, "could also accentuate Soviet fears."

In short, the statements conclude, the new missile will "entail political costs and raise difficult questions about their arms control implications."