Israel's nuclear weapons program was aided by other countries. After the Suez crisis in 1956, France agreed to help Israel build a nuclear reactor and reprocessing plant near Dimona which used natural uranium moderated by heavy water. Plutonium production started in about 1964. Top secret British documents obtained by BBC Newsnight show that Britain made hundreds of secret shipments of restricted materials to Israel in the 1950s and 1960s. These included specialist chemicals for reprocessing and samples of fissile material—uranium-235 in 1959, and plutonium in 1966, as well as highly enriched lithium-6 which is used to boost fission bombs and fuel hydrogen bombs. The investigation also showed that Britain shipped 20 tons of heavy water directly to Israel in 1959 and 1960 to start up the Dimona reactor. The transaction was made through a Norwegian front company called Noratom which took a 2% commission on the transaction. Britain was challenged about the heavy water deal at the IAEA after it was exposed on Newsnight in 2005. British Foreign Minister Kim Howells hid behind the Noratom contract and claimed this was a sale to Norway. But a former British intelligence officer who investigated the deal at the time confirmed that this was really a sale to Israel and the Noratom contract was just a charade. The Foreign Office finally admitted in March 2006 that Britain knew the destination was Israel all along.
In 1961, the Israeli Prime Minister David Ben-Gurion informed the Canadian Prime Minister John Diefenbaker that a pilot plutonium-separation plant would be built at Dimona. British intelligence concluded from this and other information that this "can only mean that Israel intends to produce nuclear weapons". By 1969, U.S. Defense Secretary Melvin Laird believed that Israel might have a nuclear weapon that year. Later that year, U.S. President Richard Nixon in a meeting with Israeli Prime Minister Golda Meir pressed Israel to "make no visible introduction of nuclear weapons or undertake a nuclear test program", so maintaining a policy of nuclear ambiguity. By 1979 U.S. Intelligence believed Israel had designs and fissile material for nuclear weapons, and were perhaps in a position so they could test a more advanced small tactical nuclear weapon or thermonuclear weapon trigger design.