The chief Soviet delegate at the East-West review conference of the 1975 Helsinki Accords today rejected western proposals to improve human rights guarantees in the final document, raising the prospect of a deadlock in the marathon 35-nation meeting.

The clash over human rights at this Conference on Security and Cooperation in Europe was underlined by the presence of Soviet exile Avital Scharansky, whose husband Anatoly is serving a 13-year term on charges of espionage and anti-Soviet propaganda.

Avital Scharansky said at a press conference that if a final document were signed in Madrid without thorough safeguards on human rights, "It would be signed over the bones of my husband and others like him."

Speaking before a conference plenary session, Soviet delegation head Anatoly Kovaliov said he would accept a draft final document proposed by neutral nations and would oppose any modifications. It was the first official Soviet response to the draft, sponsored by eight neutral nations last March, that was described by the western camp as "lukewarm" on human rights.

The West in the past weeks has suggested a number of proposals aimed at strengthening the human rights language in the final document. The proposed amendments have not been formally submitted but have been circulated to the Soviets and others. They concern family reunification and the right to emigrate, freedom of religion, the right to form trade unions and safeguards for those monitoring the implementation of the conference's accords.

Kovaliov told delegates that an end to the conference, which has been meeting here since November 1980, was overdue and that "the possibility of further negotiations is exhausted for all practical purposes."

He added: "If anyone wants to change this draft the neutral document it would lead to the rubbing out of everything positive that has been achieved at this meeting."

A senior western diplomat termed the Soviet stand "an ultimatum accompanied by a threat." Speaking after the plenary, he said the western amendments on human rights hitherto had been viewed as "an acceptable base for final negotiations."

In Washington, a source familiar with the conference said he believed that Kovaliov's statement was not the Soviets' final position and that further talks could produce a viable final document.

Avital Scharansky told reporters she had received no news of her husband since February, when authorities at the Chistopol prison, 800 miles east of Moscow, stopped his monthly letters. She said she feared he would resume a hunger strike to protest the absence of family visits and mail.

Avital Scharansky's presence at the conference received the endorsement of U.S. delegates. When the hosts asked her to leave because she had no accreditation, the Americans said she would be their guest.

Spotting her in the conference coffee room, the deputy leader of the Soviet delegation, Sergei Kondrachev, turned and made a hasty exit.

A senior member of the U.S. delegation, R. Spencer Oliver, said after the incident: "Scharansky has been unjustly punished for nothing more than seeking to join his wife in Israel. The Helsinki Final Act guarantees that right, and Scharansky was seeking to exercise it."

Oliver declined to comment when asked whether a final document could be signed in Madrid while Scharansky was still imprisoned.

Avital Scharansky, 32, last saw her husband on July 5, 1974, the day after they married, when she left for Israel after receiving assurances that he would be able to join her within six months. In 1977, Scharansky, a mathematician, was sentenced to three years in prison and 10 years in a labor camp.