From April 1975, when Kaunda visited Gerald Ford at the White House in Washington and delivered a powerful speech calling for the United States to play a more active and constructive role in southern Africa, until approximately 1984, the Zambian president was arguably the key African leader involved in the international diplomacy regarding the conflicts in Angola, Rhodesia (Zimbabwe), and Namibia. He hosted Henry Kissinger's 1976 trip to Zambia, got along very well with Jimmy Carter, and worked closely with Ronald Reagan's assistant secretary of state for African affairs, Chester Crocker. While there were disagreements between Kaunda and U.S. leaders (such as when Zambia purchased Soviet MIG fighters or when he accused two American diplomats of being spies), Kaunda generally enjoyed a positive relationship with the United States during these years.
On 26 August 1975, Kaunda acted as mediator along with the Prime Minister of South Africa, B. J. Vorster at Victoria Falls to discuss possibilities for an internal settlement in Southern Rhodesia with Ian Smith and the black nationalists. After the Lancaster House Agreement, Kaunda attempted to seek similar majority rule in South West Africa. He met with P. W. Botha in Botswana to debate this proposal, but apparently failed to make a serious impression.
Meanwhile, the anti-white minority insurgency conflicts of southern Africa continued to place a huge economic burden on Zambia as white minority governments were the country's main trading partners. In response, Kaunda negotiated the TAZARA Railway (Tanzam) linking Kapiri Mposhi on the Zambian Copperbelt with Tanzania's port of Dar-es-Salaam on the Indian Ocean. Completed in 1975, this was the only route for bulk trade which did not have to transit white-dominated territories. This precarious situation lasted more than 20 years, until the abolition of apartheid in South Africa.