WASHINGTON (AP) _ President Kenneth Kuanda of Zambia said Wednesday that South African blacks are losing patience with apartheid and the result could be a bloody civil war involving the whole region.

''Indeed, a civil war in South Africa will, I am afraid, seriously affect international relations between Africa and the Western world,'' Kuanda said in a speech at Washington's Howard University.

Kuanda, who is also the current chairman of the continent-wide Organization of African Unity, received an honorary doctorate of laws.

He urged the United States and other Western countries to apply more pressure through stronger trade sanctions and disinvestment to force an end to South African racial segregation.

Kuanda was scheduled to have talks and lunch Thursday with President Reagan. The administration contends that U.S. sanctions approved by Congress last year over Reagan's veto have not been effective.

''The argument that the application of comprehensive and mandatory economic sanctions will hurt black people is neither true nor convincing,'' said the 64-year-old African leader.

He likened it to the argument of American supporters of slavery in the 19th century ''that emancipation would hurt the slaves.''

''No price is too high to pay for freedom,'' Kuanda said. ''The black people of South Africa are prepared to suffer any consequences, including death, to rid themselves of the scourge of apartheid.''

In addition to Reagan, Kuanda planned talks with congressional leaders and other prominent Americans. They included Jesse Jackson, the Democratic presidential aspirant and civil rights leader who described Kuanda as a key figure in finding a solution to the southern Africa's problems.

Kuanda chairs the organization of leaders of frontline states bordering South Africa.

He said wealth from ''huge investments in South Africa'' by the United States, Britain, West Germany and France ''is the economic backbone which bolsters the racist apartheid regime.'' Kuanda urged those countries to apply more political, economic and moral leverage to force an end to apartheid.

''The most effective way of using this leverage it to withdraw the economic support they give to the racist regime,'' he asserted.