LOS ANGELES — Revelations in former U.S. President George W. Bush's recently published memoirs show that he declined an Israeli request to destroy Syria's secret nuclear reactor in the spring of 2007. While the revelation may appear merely to be a historical footnote, more profoundly it raises new uncertainty about whether Israel now thinks that it can rely on the United States to apply military force to stop Iran's nuclear program should diplomacy fail. The Syrian episode suggests that it cannot, which means that Israel may decide to go it alone once again, this time to eliminate Iran's nuclear facilities.

If Israel did so, however, it would confront a conundrum. Unlike the attack on Syria's nuclear plant, Israel's conventional forces do not have the capacity to destroy Iran's suspect installations. Portions of Iran's nuclear program may be too heavily bunkered, dispersed, or concealed. This raises the question of whether Israel's repeated refrain that "all options are on the table" implies that even a nuclear strike is possible. Israel's nuclear history provides no clear answer, but the future may force the issue.

Israel has never acknowledged having nuclear weapons, let alone the size and scope of its arsenal. Israeli policymakers refuse to talk about the subject. Israel's parliament, the Knesset, never discusses the program or appropriates money for it. Military censors quash public discourse about it.