A senior Sandinista military officer apparently defected to the United States last week, diplomats and politicians said today.

A Sandinista military officer who asked for anonymity described the matter as "a very high-level case."

Sandinista military officers said helicopters and fixed-wing aircraft were being used in support of ground troops.

And a post-election surge in desertions by army conscripts is a more telling expression of popular sentiment than the bluster of Sandinista officers facing loss of privileges.

An Administration official said the Sandinista officers, whom he would not identify, had said, "Yes, indeed there had been a diversion, but it had been a small one."

He acknowledged that a number of contra field commanders are former Sandinista officers, and said they would be permitted to rejoin the army after an armistice.

He described as "cordial" his relationship with the Nicaraguan Army and the police, which remain controlled by Sandinista officers.

The Sandinista officer who carried out the order to send the Bishop across the border was none other than Fernando Caldera.

She also has a sister who is a Sandinista military officer.

Sandinista officers remained at the head of all general staff directorates and military regions.