The Soviet Union violated "unmistakable language" in the 1972 antiballistic missile (ABM) treaty by beginning construction of a giant new radar in central Russia, Kenneth L. Adelman, director of the Arms Control and Disarmament Agency, said yesterday.

The sophisticated phased-array radar near Krasnoyarsk is one of "15 to 20 issues" discussed in a new presidential report to be sent to Congress today on Soviet noncompliance with arms control agreements, Adelman told reporters at a breakfast meeting yesterday.

The report also is expected to charge the Soviets with use of chemical and toxic weapons, testing a second land-based intercontinental missile, deploying the mobile SS16 missile, use of various new ABM hardware and production of too many Backfire bombers.

The congressionally required report expands on one sent to Congress in January 1983. The earlier report for the first time formally accused the Soviets of seven violations.

Yesterday, Adelman repeated the Reagan administration view that such violations cannot "be swept under the rug." He also said these violations "have to give you pause when you go into new negotiations" such as those scheduled March 12 in Geneva.

Adelman confirmed that Secretary of State George P. Shultz last month in Geneva discussed with Soviet Foreign Minister Andrei A. Gromyko the Soviet "pattern of behavior" on the ABM treaty and other agreements. Adelman said such behavior "cast a dark shadow" over the prospects for approval of arms control agreements in the United States.

He also said the "erosion of the ABM treaty" will be discussed in Geneva by the working group on defensive or space weapons. "We will pick up the dialogue begun by Shultz on reinforcing the ABM regime," he said.

Adelman said a representative of his agency had been sent to the Pentagon to make certain that the president's Strategic Defense Initiative research, "Star Wars," does not violate the ABM treaty.

He also said that this fall the administration will review its decision "to adhere to the limits" of the SALT II treaty on numbers of intercontinental missiles as long as the Soviets "show restraint."

As of now, Adelman said, Moscow has displayed "a questionable pattern," adhering to some provisions but not others.

Adelman disclosed that the Joint Chiefs of Staff are studying "the military significance" of reported Soviet violations and "whether a new military threat" has been created by any one of them. The review is part of an administration effort to determine what action to take because of the violations.

Adelman said the administration "has not received satisfaction" from the Russians when complaints about violations have been raised at the Geneva-based standing consultative commission which the superpowers set up under provisions of the SALT I treaty to discuss such matters.

Having publicized the violations, Adelman said, the administration will "ask the advice and counsel of Congress on what to do about them."

In response to a question, Adelman said the Krasnoyarsk radar is "militarily significant," not just because such a facility is prohibited by the ABM treaty, but also because of "what it portends" in Soviet ability to move quickly to a nationwide ABM system, also barred by the treaty.

A phased-array radar is composed of multiple units pointed in slightly differing directions to produce a widespread image. Such facilities are prohibited by the ABM treaty unless they are located on a nation's border, on the theory that inland facilities could be for no other purpose than missile defense. The Krasnoyarsk radar is located far inland.

Adelman also said he believes that the production and use of chemical and toxic weapons, another violation to be cited in today's report, has military significance because "it is breaking down an international norm" and leading to use of such weapons in Third World wars.

Last year's report cited the Krasnoyarsk radar as "almost certainly" a violation of the ABM treaty. The new report, sources said, will add deployment of a mobile ABM radar, rapid-reload ABM missiles and a new ABM launcher to the list of violations of the 1972 accord.

The 1983 report also charged three probable violations of the unratified 1979 SALT II treaty: electronically encoding signals from missiles being flight-tested; testing a second new land-based ICBM while the treaty allows one, and deploying the mobile SS16 missile which was outlawed by the treaty.

The new report will also add, as a violation of an agreement associated with SALT II, production of Backfire bombers above the level which the United States said former Soviet president Leonid Brezhnev agreed to in 1979.