WASHINGTON: Increasingly bogged down in the sands of Iraq, the US thrashes about looking for an honorable exit. Restoring cooperation between Washington and Tehran is the single most important step that could be taken to rescue the US from its predicament in Iraq. Understanding why requires some historical reflection.
Since the mid-1950s, US policy in the Middle East and Persian Gulf region was implicitly based on three pillars – Israel, Iran and Saudi Arabia. As the British withdrew, Washington established nervous but lasting ties with Saudi Arabia. At the same time, the US built strong relations with the shah of Iran. After 1948, when it recognized the new state of Israel, the US slowly became a guarantor of that new state's survival. London's role in the entire region became marginal, especially after the Suez crisis in 1956, when President Dwight Eisenhower abruptly stopped the joint British-Israeli military operation to seize the Suez Canal.
Thus by preventing any of the three camps from overrunning the other, the US provided regional stability.
Whether American leaders employed this strategy by design or by trial and error is arguable. At the time, they were more concerned with the Soviet challenge, trying to organize the so-called "northern tier," i.e., with Turkey, Iran and Pakistan, as a barrier to Soviet influence. They probably did not foresee they had undertaken an equally demanding task of sublimating two major intra-regional quarrels, virtually irresolvable ones.
http://yaleglobal.yale.edu/display.article?id=9223