The Reagan administration said yesterday it was "very disturbed" by the rising level of violence in South Africa that has led to the imposition of a state of emergency and called upon the government there to exercise its "considerable responsibility" in the present crisis "in a scrupulous manner."

White House spokesman Larry Speakes said the administration regarded South Africa's system of rigid racial segregation, known as apartheid, as "repugnant and largely responsible for the current violence."

"The period of violence must be ended," he said, "so that South Africa can proceed into a meaningful political dialogue which would lead to basic reforms, moving away from apartheid."

Despite the deteriorating situation in South Africa and groundswell of criticism in Congress over the administration's policy of "constructive engagement," Speakes gave no indication that the White House was considering a reassessment that might result in any change in objectives or tactics.

He denied that the latest U.S. admonition to South Africa signaled a shift. "The United States policy is still to remain in close touch and work closely with the South Africans and make our views known to them on a continuing basis," he said.

A State Department spokesman was more explicit.

"We are not reviewing the policy and there is no intention of reviewing the policy," he said. "We continue to think the objectives of our policy are correct."

Privately, some administration officials say they believe that the policy of constructive engagement is "unraveling," as one of them put it.

"There is a lot of hard thinking going on, but I don't think I would call it a reassessment," one U.S. official said. "After all, what are the options?"

Speakes refused to say whether the administration felt the state of emergency imposed Saturday should be lifted, limiting his comments to a prepared statement. The statement said: "The South African government bears a considerable responsibility at this time. It says it seeks to restore law and order and that is understandable. But we look to the South African government to exercise its responsibilities in a scrupulous mannner."

Speakes did not indicate what he meant by "scrupulous manner." But a State Department spokeman called upon Pretoria to respect the fundamental rights of "all" its citizens and to open negotiations with its majority black population.

On June 14, following a South African raid into neighboring black-ruled Botswana, the administration recalled the U.S. ambassador to South Africa, Herman W. Nickel, for what it called "consultations to review the situation."

Earlier in May, the South African government had sent a commando team into northern Angola to blow up that country's main oil production center, which is partly owned and operated by the U.S. Gulf Oil Co., now a Chevron Corp. subsidiary.

The team was intercepted by Angolan troops, aborting the mission.

The administration expressed its outrage at the incident, which served to undermine its efforts to negotiate with South Africa and Angola a peaceful transition to independence for the South African-administered territory of Namibia. The talks halted after the House, like the Senate, voted to lift a ban on aid to Angolan rebels, and the Marxist Angolan government reacted by ending its participation.

These developments, together with the continuing violence inside South Africa that has taken the lives of about 450 people, mostly blacks, in the past 10 months, have increased congressional and public pressure on the administration to rethink its constructive-engagement policy.

The thrust of this policy is to rely on quiet diplomacy to try to persuade the South African government to change its ways, end apartheid and leave Namibia. The administration continues to oppose strongly the imposition of any kind of economic sanctions such as the House and Senate have voted for by large margins.

After a Senate vote July 11 in favor of a ban on new bank loans and and the sale of nuclear technology to South Africa, Speakes said the administration believed that sanctions were "the wrong way to bring about changes we all desire to see" in South Africa.