A US official disbelieved Israel's assurances during the Cold War that it would avoid acquiring nuclear weapons and feared the United States' main ally in the region would spark a Middle East nuclear arms race, documents from that time show. A 1969 memo reported intelligence findings that "Israel is rapidly developing a capability to produce and deploy nuclear weapons," despite promises it would not introduce nuclear arms to the region. The memo by Joseph J. Sisco, an assistant secretary of state, was contained in 50,000 pages of previously secret papers from Richard Nixon's presidency, released Wednesday by the National Archives. The collection draws heavily on national security files during the Vietnam War, arms control negotiations with the Soviets, and the intense superpower competition for influence in the Middle East and beyond. To this day, Israel officially neither confirms nor denies its nuclear status and the actual size of its stockpile remains uncertain. But it has long been considered the only nation in the Middle East with atomic weapons. Researcher William Burr said the memo on Israel's nuclear program sheds light on a little known area of US intelligence. "For a long time, the US kept secret its assessment of the status of the Israeli nuclear program," said Burr, senior analyst at the National Security Archives at George Washington University. The paper shows "Israel could develop nuclear weapons fairly quickly, something that isn't widely known." In the memo, Sisco urged Secretary of State William Rogers to try to curb Israel's ambitions before it was too late. "If this process continues, and it becomes generally assumed that Israel has the bomb, it will have far-reaching and even dangerous implications for the US," Sisko wrote. Among those dangers: "Israel's possession of nuclear weapons would do nothing to deter Arab guerrilla warfare or reduce Arab irrationality; on the contrary it would add a dangerous new element to Arab-Israeli hostility with added risk of confrontation between the US and USSR." Sisco said a nuclear-armed Israel would draw Arab states even closer to Moscow and perhaps under a "nuclear umbrella" extended by the Soviets.