The United States is dismantling top secret intelligence-gathering equipment in Iran because of the political instability there, government sources said last night.

The dismantling, with removal likely later, could complicate President Carter's efforts to sell a strategic arms limitation treaty (SALT) to the Senate becahuse much of the gear keeps track of what the Soviets are doing with their strategic weaponry.

Central Intelligence Agency gear in Iran for years has tracked the flights of Soviet missiles and intercepted their telemetry (electronic signals) on the missiles' performance. Such information is considered vital for the United States to verify that the Soviets are living up to strategic arms control agreements.

Asked yesterday if it was removing intelligence equipment from Iran, the CIA refused to comment.

Other sources, however, said the dismantling and storing of CIA eavesdropping and tracking gear in Iran had already started.

But the fact that the top secret equipment has not been removed from Iran, they said, is enabling government spokesmen to postpone a public discussion of the polittical and military implications of such a step.

"It has grave implications for SALT II verification," one knowledgeable source said.

Charges that the Soviets cheated under SALT I by encoding their missile telemetry has put pressure on the Carter administration to improve the verification features of any new strategic arms agreement. The loss of the Iranian monitoring stations would make it hardr for the administration to assure Congrees that the United States could detect any future Soviet cheating.

Losing Iran as an intelligence-gathering base would e another blow to the beleaguered CIA. The United States' other big intelligence collector, the National Security Agency, does most of its monitoring of Soviet military activities from posts in Turkey.

The United States also has ilstening posts in West Germany and elsewhere as well as satellites that look down on the Soviet Union from space to help keep track of strategic missile tests and other military activities.

Besides dismantling some of the CIA intelligence gear, government officials yesterday were discussing the possibility of increasing the force of U.S. guards around installations still intact.

At a Pentagon briefing yesterday, spokesman Thomas B. Ross said "no" when asked if the United States was removing "any sensitive intelligence-gathering equipment from Iran." Other sources said dismantling and storing the gear in safer places in Iran had begun.

Ross also said that no sophisticated American military equipment -- either U.S. or Iranian-owned -- has been removed from the country. Among the advanced weapons there are 77 Navy F14 fighter planes, which would make quite an intelligence coup for the Soviets if they were able to get possession of them.

The F14 is one of the world's most advanced aircraft, having highly secret missiles and electronic gear. It is far more sophisticated than the most advanced Russian plane, the Mig259

The Defense Department contends that the F14 and other U.S. weapons are salfe and need not be removed.

Ross maintained this position yesterday, saying there are no plans to fly out the F14s or remove other sensitive equipment. However, the dismantling of intelligence gear may mark the beginning of a shift in that position.

U.S. officials focusing on the political turmoil in Iran remained gloomy about the future there last night, with one predicting instability for years to come, not just months.

The Pentagon regularly flies giant C5 transports into Iran loaded with supplies. The planes, which on the return trip now fly goods and people to Ramstein, Germany, and then to the United States, could be used to evacuate sensitive intelligence equipment and weaponry.

The C5 was pressed into service yesterday to help combat a problem in Iran that had nothing to do with the political crisis -- unusually cold weather.

The Pentagon said that Iran had ordered $10 million in cold weather clothing and insulated food containers for 25,000 military personnel. Ross described the airlift as "an emergency shipment."

The airlift that began yesterday involves six C5 and four C141 transports flying from Richmond, Va.; Dover, Del., and Memphis, Tenn., to Iran. The Pentagon said 260 tons of cold weaather gear will be airlifted.

The Pentagon said Iran is paying for the equipment and the cost of airlifting it.