U.S. arms control director Fred C. Ikle cautioned yesterday againat basing American nuclear strategy on estimates of Soviet military intentions, which he said "are not fixed."

"We shouldn't go around asking ourselves, 'are the Russians planning superiority'; 'are they planning a first strike,'" Ikle, head of the Arms Control and Disarmament Agency, told the Senate Foreign Relations Committee.

"I think it is an uncertainty in their mind," Ikle said.

The Soviet Union, he said in effect, will do what it believes it can get away with doing, with its actions depending on the strength and capability and will of the United States.

In farewell testimony on his experience and views as director of the arms control agency, Ikle blamed the failure to achieve a new accord in the nuclear Strategic Arms Limitation Talks (SALT) on Soviet intransigence, rather than on "alleged dissension within the administration."

Secretary of State Henry A. Kissinger, who was in disagreement with the Defense Department and with Ikle's agency on SALT strategy, privately has blamed internal disagreement as a major reason for delay.

President Ford, said in a Jan. 7 interview with The Washington Post that "it was a combination" because "We were faced with two problems: one was some honest disagreement within the administration on the one hand; and some nonresolvable differences with the Soviet Union on the other."

Ikle's assertion yesterday was that, if anything, the U.S. position was too flexible, not too firm.

"On the controversial issue of cruise missiles and the new Soviet bomber," Ikle said, "we offered five different solutions within as many months, between last fall and early spring this year."

"In retrospect," Ikle said, "perhaps we took too many initiatives, giving our adversaries the impression that they could wait us out."

Sen. Charles H. Percy (R-Ill.), who proposed the hearings which began yesterday, said that "there is honest and strongly felt disagreement on Soviet intentions" among U.S. officials. Percy said he was concerned about reports that the new U.S. National Intelligence Estimate shows that the Soviets are "seeking superiority."

However, Sen. Dick Clark (D-Iowa) said, "It's my impression that the recent Soviet intelligence estimate concludes that the Soviet Union is not trying to achieve superiority," but rather it is "Team B that has come to that conclusion."

In the recent estimation process, a team of outside panelists was used to challenge the views of the official analysts, known as Team A. Percy said the committee will hear outgoing Central Intelligence Agency Director George Bush in closed session on Tuesday, to try to clarify the controversy over the top secret estimates.

A principal argument in hardening U.S. estimates of Soviet intentions, Clark noted, is that the Soviet Union is engaged in a massive civil defense program, to survive a nuclear war.

Ikle said the Soviet civil defense is "puzzling and disturbing." But he would "not put so high a priority" on its implications and effectiveness as some U.S. specialists, because no one "could predict what could happen in a mass nuclear war."

However, Ikle said, "We have to ask whether our long-term objectives for arms control and disarmament are shared by the Soviet leadership." That was a central argument of the more pessimistic Team B, in the internal intelligence debate.