France was Israel's primary arms supplier and one of her closest allies, at the time. France happened to be working on their own nuclear capabilities (still in its early stages at this point), and they offered to help Israel build a nuclear reactor after Shimon Peres convinced them of the threat Nasser posed to Israel. Guy Mollet, then the French Prime Minister, felt he personally owed Israel the bomb, as a duty to his fellow socialists there, who he felt he had abandoned.

Basically, Israel and France were very close allies at the time, and the perceived threat to Israel's existence prompted France to supply them with a reactor. This policy in France would change, however, with the presidency of Charles de Gaulle, who was very critical of Israel, and French assistance ended in 1966.