Soviet authorities are harassing American diplomats with small-scale administrative irritants, including cutbacks in parking privileges and even an impromptu change of the embassy telephone number, U.S. sources said here today.

They said the moves are believed to reflect a general deterioration in U.S. Soviet relations that began after the Soviet invasion of Afghanistan last December and the subsequent U.S. boycott of the Moscow Summer Olympics.

An official said the change of the phone number, "on short notice," took place this week without any public announcement. Hence people seeking to call the embassy, particularly Soviets seeking information on emigration, have been inconvenienced.

Another apparently sudden Soviet decision involves converting the parking facility of the U.S. Consulate in Leningrad into a park.The move was said to have been made for "environmental reasons," but the U.S. sources said Soviet authorities just as suddenly posted no-parking signs on both sides of the street where the consulate is located, making access for U.S. personnel more difficult.

At least one U.S. diplomatic vehicle parked in front of the consulate was hauled away, in violation of the accepted practice in both countries.

[A State Department official in Washington said there was no known recent precedent in the United States, such as the towing of a Soviet envoy's car or restriction of parking privileges, to explain the actions in Moscow.]

The U.S. officials said the Soviets also have initiated protracted visa delays for American support personnel and have raised additional difficulties concerning shipments of construction material for the new U.S. Embassy.

The arrival of 15,000 containers with pipes, wiring and other construction material has been delayed because of a reported dispute over inspection.

Under an embassy construction agreement, the United States was permitted to build the interior of the new structure -- a measure deemed necessary to keep out listening devices. U.S. officials say that the agreement does not provide for Soviet inspection of the containers with the construction material.

Officials also said the number of Soviet security personnel stationed around the embassy building has increased noticeably and that occasionally U.S. personnel are asked to show identification papers before being allowed to enter the nearby offices of the U.S. trade mission.

These and other unspecified irritants reportedly have cropped up since the end of the Summer Olympics. U.S. diplomats say the measures are not believed to be connected with Moscow's decision to resume jamming of the Voice of America and other Western broadcasts. That decision clearly was tied to the current labor unrest in Poland and efforts to prevent the spread of ideas current there to the Soviet Union.

Westerners say, however, that the diplomatic climate here has chilled in the past several weeks.