WASHINGTON, Nov. 28 — In July 1969, while the world was spellbound by the Apollo 11 mission to the moon, President Richard M. Nixon and his close advisers were quietly fretting about a possible nuclear arms race in the Middle East. Their main worry was not a potential enemy of the United States, but one of America’s closest friends.

“The Israelis, who are one of the few peoples whose survival is genuinely threatened, are probably more likely than almost any other country to actually use their nuclear weapons,” Henry A. Kissinger, the national security adviser, warned President Nixon in a memorandum dated July 19, 1969.

Israel’s nuclear arms program was believed to have begun at least several years before, but it was causing special fallout for the young Nixon administration. For one thing, President Nixon was getting ready for a visit by Prime Minister Golda Meir of Israel, who was also in her first year in office and whose toughness was already legendary.

Should Washington insist that Israel rein in its development of nuclear weapons? What would the United States do if Israel refused? Perhaps the solution lay in deliberate ambiguity, or simply pretending that America did not know what Israel was up to. These were some of the options that Mr. Kissinger laid out for President Nixon on that day before men first walked on the moon.