Following the release of the NIE report claiming that Iran's nuclear program stopped in 2003, this justification goes out the window.
Gerald M. Steinberg discusses this and other developments in Israel's relationship with the US. Here is the summary of the article:
The Bush Visit and Tensions in the U.S.-Israel RelationshipRead the whole thing.
* The December "surprise" resulting from the publication of the U.S. National Intelligence Estimate disrupted fifteen years of Israeli policy based on working with the international coalition to pressure Iran to drop its nuclear weapons program through sanctions and the threat of military action, and has reminded Israelis of the limits of American security guarantees and strategic cooperation.
* Within two weeks following publication of the NIE report, China signed a major contract on energy development and supply with Iran, and Russia quickly dispatched two shipments of nuclear fuel for the Bushehr nuclear reactor. Egypt moved to improve relations with Iran, and Saudi Arabia welcomed Iranian President Ahmadinejad to Mecca for the Haj.
* Prime Minister Olmert had explained the logic of the "Annapolis process" in terms of the coalition to stop Iran, but two weeks after Annapolis, with the release of the NIE report, this rationale has lost much of its relevance.
* Another source of stress comes from differences over renewed U.S. efforts to forge a quick agreement with the Palestinian Authority at a time of continued terrorism, the violent conflict between Fatah and Hamas, the failure to develop functioning Palestinian institutions, and the PA's ongoing incitement and rejection of the legitimacy of a Jewish state.
* In addition, the overall decline of U.S. influence, as reflected in Iraq, the return of Russia as a world power, the chaos in Pakistan, and other developments, has highlighted the limits of Israeli reliance on American assistance, and the need for Israel to maintain an independent capability to act when necessary.