U.S. intelligence agencies have concluded that the Soviet Union is moving faster than expected to develop and deploy new strategic missile systems, according to informed sources.

The conclusions of a "National Intelligence Estimate," which intimates that Moscow may be poised to begin an ambitious round of new missile deployments, will be included in President Reagan's report to Congress today on future U.S. adherence to the unratified SALT II treaty, the sources said.

As reported earlier, the president is expected to announce today that the United States will continue to adhere generally to the limitations of SALT II but will make "proportional responses" to what it determines to be Soviet violations of the pact.

Given the new intelligence estimate, some sources say Reagan may link continued U.S. adherence to the SALT II limits after the treaty expires at year's end to some sign of Soviet restraint in these new missile programs and to steps ending what the United States considers Soviet violations of SALT II.

The new intelligence estimate reportedly concludes that the growth in quality and quantity of Soviet intercontinental ballistic missiles appears to be faster than anticipated and that two additional large missiles may be flight tested within the next year.

One of the larger ICBMs is looked upon as an updated version of the SS18, but the other may be a new type prohibited by SALT II.

The United States has observed only testing of solid-fuel engines for this second rocket, so little is known of its eventual configuration. A new solid-fuel Soviet ICBM would violate SALT II.

In any case, new ICBM production could put the Soviet Union over the SALT II limits relatively quickly unless it takes steps to eliminate large numbers of old silo-based ICBMs and scrap older submarines, as it has done in the past. In a letter to Reagan last week, Republican Sens. James A. McClure (Idaho), Jesse Helms (N.C.) and John P. East (N.C.) identified the National Intelligence Estimate as NIE-11-3-8-85 and said it indicated "a dangerously worsening state of Soviet military supremacy." The three legislators called on the president to give it "the widest possible distribution in Congress . . . . "

The Soviets increased the number of their ICBM warheads from approximately 5,500 in 1979 to about 9,200 as of last year, growth that was permitted by SALT II. They could add another 2,000 warheads and still remain within treaty provisions, according to a study by the Federation of American Scientists, a group that supports keeping the SALT II limits.

The president has already charged that Moscow violated the SALT II agreement by producing more than one permitted new missile and by hiding information on its ICBM tests.

Reagan is expected to announce the first "proportional response" today -- what will be done this fall when a new Trident submarine carrying 24 strategic missiles goes on sea trials, taking the United States 14 missiles over a SALT II limit.

Sources said an older U.S. Poseidon submarine, the USS Sam Rayburn, with 16 missiles, will be removed from active service as a launcher of ballistic missiles. But the process of destroying the sub, as required by the treaty, will not begin.

Instead, the United States will take advantage of the six months' leeway that is allowed on destruction of missiles to determine what the Soviets do in the Geneva arms negotiations and what they do with their missile systems.

The announcement today is expected to settle, if only for the time being, a basic disagreement between Secretary of State George P. Shultz and Defense Secretary Caspar W. Weinberger.

Shultz initially proposed continued adherence to the treaty and a supplemental defense spending request to Congress to show resolve in the face of the Soviet violations.

Weinberger proposed that the president announce that the United States would let the treaty expire, but would not make any immediate change in the size of the U.S. strategic forces or the pace of their modernization.

In the end, sources said, national security affairs adviser Robert C. McFarlane adapted an "adherence-with-exceptions" approach first suggested by Paul H. Nitze, the president's special adviser on arms control, and Kenneth L. Adelman, director of the Arms Control and Disarmament Agency.

Supporters of the Shultz position pointed out yesterday that the decision does not put the United States in violation of the treaty for the time being and, in effect, continues the policy of observing the unratified treaty. It also allows time for the Soviets to respond before a next step is taken.

Weinberger aides said they were disappointed that the views of the NATO allies and Congress played more of a part in the president's decision than the apparent growth in Soviet strategic weapons.

Echoing a letter Weinberger sent Reagan on Friday, one aide said Moscow may take the approach as "a sign of weakness," since the president had been prepared to abandon the treaty before the outside pressure was applied.

Georgi Arbatov, a member of the Soviet Communist Party's Central Committee, said yesterday the president's approach would make arms control "more shaky" but would not have a major effect on current negotiations.

"I don't think that life will stop with the declaration," Arbatov said on CBS' "Face the Nation."

One source said the Weinberger-Shultz dispute will carry over to the interagency body that will have to determine appropriate "proportional responses" to Soviet treaty violations.