Zambian President Kenneth Kaunda said Monday that Rhodesian Prime Minister Ian Smith has tried to resign three times, but has been prevented from doing so by South African Prime Minister John Vorster.

Repeating to reporters what he had earlier told Andrew Young, the U.S. ambassador to the United Nations now touring Africa, Kaunda said his information came from "very, very reliable sources." He declined to identify them or indicate when the resignations may have been tendered.

"You will jolly well stay there until I have solved my problem" in Namibia (Southwest Africa), Vorster was quoted as telling Smith, who was cast as a pawn in South African foreign policy.

South Africa is currently negotiating the future independence of Namibia with the five Western members of the U.N. Security Council: the United States, Britain, France, West Germany and Canada.

"Vorster is doing this," Kaunda said, because he "believes that if the West can accept his conditions on Namibia, he will be able to deliver Smith to them."

American officials have reported substantial recent progress with the South Africans on Namibia, but many obstacles are said to remain. The talks are tentatively scheduled to resume in Cape Town before the end of the month.

Kaunda's remarks reflected the general conviction in Black Africa that Vorster can call the tune in Rhodesia because Smith depends on South Africa for oil and other vital imports.

Kaunda reportedly asked Young to pass on to President Carter Zambia's oft-repeated desire that the United States force Western oil companies to cut off deliveries to Rhodesia. Since Mozambique shut its border with Rhodesia last year, and closed off the pipeline that ran from the port of Beira to Umtali in Rhodesia, the Smith regime has relied on South Africa for all oil supplies.

Kaunda charged that Western oil companies - apparently Shell, British Petroleum, Mobil, Caltex and the Compagnie Francaise des Petroles - that have been providing Rhodesia with oil recently "met to consider how they could destroy the documentary evidence of their dealings."

Kaunda has announced his intention to bring court action against the companies for violating United Nations sanctions prohibiting trade with Rhodesia. So far, he has not announced where or when the action would be brought.

"But they are late," he said of the oil companies, "because we have sufficient evidence already with the help of Lonrho." Lonrho is a London-based, part-Kuwaiti-financed mining and industrial conglomerate with more interests in black than in white-dominated Africa. Among its many holdings is the Beira-to-Umtali pipeline.

Lonrho Managing Director Tiny Rowland is a close personal friend of Kaunda's.

American officials have expressed doubts about the effectiveness of an oil embargo against Rhodesia. They noted that a South African law prohibits any South African-based company or subsidiary of a foreign-owned multinational from divulging import and export data. Moreover, Rhodesian oil requirements are so small as to be virtually indistinguishable in the mass of South African oil imports.

Kaunda placed his 5,000-man army on alert last week after Smith warned that Rhodesia might invoke the right of pursuit against Zambian-based guerrillas. He said today, "I believe we are able to defend ourselves."

Less than two months after Soviet President Nikolai Podgorny's visit here, Kaunda repeatedly praised President Carter and said, "We understand what he has been doing and saying" should give him a chance."

"We should not dismiss him as just another Westerner," he said, "we should give him a chance."

Young, who met with Kaunda today before leaving for Khartoum, Sudan, the last stop on his African tour, drew some jeers and catcalls when he met with students here last night. There was laughter when one student yelled out that all the United States is doing for blacks in South Africa and Rhodesia is "talking." There was more laughter when Young praised Kaunda, one of Africa's more moderate leaders. Kaunda had cut student stipends in half the day before Young arrived.

In a statement today, Young said that the United States will "use methods at our disposal to push the South Africans" toward majority rule. He did not specify what methods he was referring to.

[TEXT OMITTED FROM SOURCE] inflammatory statements, said Interior Minister Connie P. Mulder. He said Young failed to keep the bargain, and the government is taking the matter "in a serious light."

During the weekend visit Young called for an economic boycott to force change in the white government's racial policies. He also embraced a black nationalist leader and reportedly sent a personal note to Winne Mandela, wife of jailed black nationalist Nelson Mandela.