Israel described as baseless on Monday reported findings in a new book that it offered to sell nuclear warheads to South Africa in 1975.
Waldo Stumpf, the former head of South Africa's Nuclear Energy Corporation, who led the project to dismantle the country's nuclear weapons program, said he doubted Israel or South Africa would have contemplated a deal seriously.
"To even consider the possible international transfer of nuclear devices ... in the political climate post the 1974 Indian 'peaceful' explosion, would have had very serious international complications," he said, referring to India's first nuclear test blast.
Britain's Guardian newspaper said documents, uncovered by a US academic researching Israel's ties with South Africa's then-white minority government, provided the first official documentary evidence that the Jewish state has nuclear arms.
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Israel is widely believed to have built more than 200 atomic warheads at its Dimona reactor but it maintains an official policy of "ambiguity" over whether it is a nuclear power.
The Guardian said documents declassified by South Africa's post-apartheid government at the request of the academic, Sasha Polakow-Suransky, included top-secret minutes of meetings between senior officials of the two countries in 1975.
Those papers, the newspaper said, showed that South Africa's defense minister at the time, P.W. Botha, asked for nuclear warheads and his Israeli counterpart Shimon Peres, now Israel's president, offered them in "three sizes."
In an official response to the report, a statement from Peres' office said: "Israel has never negotiated the exchange of nuclear weapons with South Africa. There exists no Israeli document or Israeli signature on a document that such negotiations took place."
It said there was "no basis in reality for the claims" published in the Guardian and the newspaper's conclusions were "based on the selective interpretation of South African documents and not on concrete facts."
According to the Guardian report, a nuclear sale did not go ahead, partly because of the cost.
South Africa completed its first workable nuclear device in 1979 and eventually had six nuclear devices, which were dismantled by June 1991.
Speculation about Israeli-South African nuclear cooperation was raised in 1979 when a US satellite detected a mysterious flash over the Indian Ocean.
The US television network CBS reported it was a nuclear test carried out by the two countries. But the US Central Intelligence Agency, in a document written in 1980 and released in 2004, said the United States could not determine "with certainty the nature and origin of the event."