The State Department's special consultant on the bug-ridden U.S. Embassy in Moscow said yesterday that he has recommended rebuilding the top three floors of the chancery and erecting a new six-story annex, a development that would require at least an additional $35 million and the renegotiation of a 1972 U.S.-Soviet accord on construction terms.

James R. Schlesinger, the former CIA director and defense secretary who was appointed in January to examine Moscow embassy security, told the Senate Budget Committee and a House Appropriations panel that assuring a secure chancery building will "depend upon greater cooperation from the Soviet Union than has ever been exhibited heretofore."

The Soviets, he predicted, will insist that any changes in the 1972 accord be made "on an equal basis and {that} it must apply to both sides. If the United States builds a 38,000-square-foot annex, then they must have an equivalent right to build that," Schlesinger said.

State Department spokesman Charles E. Redman said yesterday that Schlesinger's recommendations "laid the foundation for what we believe is a workable plan."

Soviet diplomats have said they want to build at least one additional new building at their new embassy complex on Mount Alto on Wisconsin Avenue; the diplomats said they will demand this and other concessions if the United States seeks to renegotiate the 1972 construction agreement.

Schlesinger's nine recommendations raise the prospect of prolonged new negotiations between Washington and Moscow on completion of the two embassy complexes, which diplomats of both countries have already occupied except for the two unfinished chancery buildings, which contain the principal diplomatic offices.

The former CIA director predicted the success of such talks would depend primarily upon the Soviets' assessment of "the international climate" and whether they decided it was worth pursuing "this secondary matter when they have much greater things at stake," such as arms control negotiations and getting into their own new chancery in Washington.

The Senate and House are expected to vote today or Wednesday on a supplemental money bill, which contains a Senate amendment calling for the total demolition and reconstruction of the new U.S. chancery.

Schlesinger, who submitted his recommendations to Secretary of State George P. Shultz on Friday, said that if the United States could obtain "full Soviet cooperation" in renegotiating the agreement and then assemble "the necessary resources," the project could be completed by 1990.

The "resources" he was referring to involve the use of U.S. construction personnel and American-made, prefabricated construction materials, which Schlesinger has recommended be used exclusively for the top three floors of the eight-story chancery and the annex. The lower The proposals raise the prospect of prolonged negotiations.

five floors could be used for unclassified and less sensitive U.S. government business without a major overhaul, Schlesinger added.

The 1972 agreement, however, requires the United States to use a Soviet construction company and a method of precasting the concrete walls and floors away from the construction site.

It was these terms that allowed the Soviets to implant sophisticated electronic devices and turn the chancery into what congressional critics have described as a gigantic antenna plugged into the KGB.

Schlesinger acknowledged that the use of U.S. materials and builders was a "precedent" the Soviets are likely to protest. But, he added, it is "a precedent whose time has come."

Schlesinger, who went to Moscow to examine the chancery, said the Soviets had "extensively permeated" it with "a full array of intelligence devices for which we do not yet understand either the technology or the underlying strategy." He said the Soviet investment in research and development of the devices "probably far exceeds" the $23 million the United States has spent on the chancery building so far.

He gave varying estimates of the cost for repairing the damage, telling the Senate Budget Committee it would probably take $40 million in addition to the $192 million already appropriated for the embassy complex. Later, he told a House panel it would require only $35 million in additional funds, roughly $20 million to build the annex and $15 million to tear down the top three chancery floors.

However, Deputy Secretary of State John C. Whitehead gave the Senate committee "a very preliminary guess" of $43 million, a figure he said was equal to the amount of unspent funds from the $192 million already appropriated.