A Central Intelligence Agency source in Moscow, described by agency officials as "an asset" who has provided information to the United States in the past, has disappeared during the last month, a source in the intelligence community said yesterday.

The source said the disappearance in Moscow may be related to the breach of highly classified information by a former CIA clandestine service officer, Edward Lee Howard, 33, who fled his home in New Mexico two weeks ago after he was identified as a Soviet spy by a high-ranking KGB defector.

However, the source cautioned, "the asset's disappearance is not necessarily linked to Howard. An awful lot of things have happened in the last few months."

Referring to reports that a Soviet official working for the CIA was presumed executed based on revelations by Howard, the source said, "It's a long jump from 'disappearance' to execution. It's not particularly unusual not to hear from someone for a length of time."

The source said that because the CIA "asset" disappeared "in rough proximity" to the identification of Howard as a Soviet agent, intelligence officials assume there may be a connection.

A source familiar with CIA penetration of the Soviet hierarchy said yesterday that Howard could have known the names or identifying characteristics of Soviet officials who provide information to the CIA. He also would have been familiar with the "trade craft" used to communicate with Soviet officials, the source said, including clandestine "drops" and use of special electronic equipment in Moscow.

The source said historically that the CIA had acquired valuable assets in Moscow, but had never been able to penetrate the ruling Politburo or its staff.

Howard was identified as a Soviet agent by Vitaly Yurchenko, a high-ranking official of the KGB who defected to the West in early August on a visit to Rome. Yurchenko is said to be undergoing debriefing by the CIA at an undisclosed location near Washington.

An FBI affidavit unsealed Friday in Albuquerque said that after Howard was dismissed from the CIA in June 1983, he traveled to Austria 15 months later and met with "senior officials" of the KGB and provided, in exchange for an undisclosed amount of money, classified data about intelligence sources and methods. An intelligence source said the meeting took place in Vienna.

During the same period, Howard met at another location in Austria with two former colleagues who were then employed by the CIA. Howard told the CIA officers that a year earlier, not long after his dismissal, he had contemplated walking into the Soviet Embassy in Washington to disclose U.S. intelligence secrets, but had decided against it.

Howard was reportedly angry over his dismissal, which occurred after he failed a polygraph examination.