Angolan President Jose Eduardo dos Santos accused the Reagan administration today of encouraging domestic brutality by South Africa's "racist regime" and helping to sabotage regional peace efforts. But he appeared to leave the door open for a resumption of talks with Washington and Pretoria on security in southern Africa.

In a carefully worded address to delegates of the Nonaligned Movement meeting here, dos Santos criticized South Africa for not giving "practical signs" of a serious intent to negotiate a regional peace settlement.

At the same time, the Marxist leader called on U.S. public opinion to oppose the recent congressional action lifting a ban on American aid to Angolan guerrillas battling his government.

Dos Santos' comments followed similar statements to reporters Monday by Vice Foreign Minister Vanancio de Moura that ended nearly two months of official Angolan silence on the issue since Luanda broke off the talks with Washington and Pretoria in protest of the July 9 vote in Congress.

The statements were widely interpreted by diplomats and other observers here as an indication that Angola would like to revive the peace process provided a way could be found for the United States and South Africa to accept responsibility for the breakdown.

According to a nonaligned diplomat, the Angolans "really don't have much choice" other than to seek some face-saving way out of the impasse that has brought regional peace efforts virtually back to where they were when they began in 1981.

This diplomat and others also noted that dos Santos appeared to depart in his speech from his standard pro-Soviet formulation on several foreign policy issues that vex the Nonaligned Movement.

Although the 105-member movement is theoretically neutral, Cuba and Vietnam have strong military and foreign policy ties to the Soviet Union and normally promote Soviet positions at its meetings. Angola is hosting this week's gathering of nonaligned ministers, and there has been widespread curiosity as to how dos Santos' welcoming speech would deal with such subjects as Afghanistan, where the movement is divided over Soviet military occupation, and Cambodia, where the pro-Soviet Vietnamese Army is at war with forces backed by the West and China.

Despite Angola's military dependency on Cuba and the Soviets, however, dos Santos did not even mention Cambodia. On Afghanistan, he merely noted "the outstanding mediation role by the United Nations secretary general warranting continued confidence . . . with the view to finding a just and equitable solution."

This possibly symbolic move away from Soviet positions coincides with an apparent desire by the currently dominant faction in the Angolan government, led by dos Santos, to address major economic and military problems by broadening its range of contacts.

Participation in the U.S.-led regional peace talks was seen as part of that effort.

For 4 1/2 years, the Reagan administration has tried to negotiate a comprehensive agreement that would lead to the withdrawal of the estimated 25,000 Cuban troops here, along with independence of neighboring Namibia from South African control.

A breakthrough in the talks came last year, when Angola and South Africa agreed to form a joint military commission that would monitor the withdrawal of Pretoria's troops from southern Angola. The South Africans have staged frequent raids into Angolan territory, arguing that they were pursuing Namibian guerrillas of the South-West Africa People's Organization.

Last fall, further progress was seen when Angola proposed a timetable for Cuban withdrawal that the administration described as flawed, but a step forward.

Angola's position is that since that time it has been badly used by both the United States and South Africa.

Last July came the congressional vote repealing the Clark Amendment, which since 1976 had prohibited U.S. aid to South African-backed guerrillas seeking to overthrow the Angolan government.

The administration did not oppose the vote, and Angola broke off negotiations, issuing a terse declaration that Pretoria and Washington clearly were working together "to destabilize the legitimate governments of southern Africa."

In his speech today, dos Santos said armed conflict between his government and guerrillas of the South Africa-backed UNITA movement, is "not a civil war . . . but multifaceted external aggression plotted by the Washington-Pretoria axis." Dos Santos blamed both Pretoria and Washington for repression of the black majority in South Africa and said abolition of apartheid "would necessarily entail the application of mandatory economic sanctions against South Africa."

However, dos Santos then "reaffirmed" that the Cuban-withdrawal proposals made last November are "still valid and germane."

He said that "no talks or negotiations can have any meaning unless they take place in a climate of relative confidence, with seriousness and in a constructive spirit."