A 54-year-old Soviet engineer and his mother drove their car into the U.S. Embassy compound yesterday despite police efforts to stop them. They left 3 1/2 hours later and held a news conference on the busy Moscow boulevard outside the embassy without any obvious police harassment, reported Washington Post correspondent Dusko Doder.

The security officials had initially brought heavy reinforcements around the American compound. But after protracted negotiations between U.S. diplomats and two Soviet officials, the reinforcements were withdrawn along with scores of vehicles positioned in the area.

If Vasily Nazarov and his 74-year-old mother Natalia are not harassed in the coming days, it could be the first instance of American and Soviet officials finding a mutually acceptable means of dealing with the increasingly frequent cases of Soviets seeking refuge in the U.S. mission.

Nazarov left his telephone number in the city of Solichnogorsk for correspondents to check on his whereabouts. He said he was being persecuted by the authorities and had been fired from a number of jobs. He alleged that his wife and another man who stood up for Nazarov were beaten by security agents.

Previous complaints to Soviet authorities were ignored, he said. U.S. officials said the pair did not show a desire to stay in the embassy or to seek political asylum.