In less than forty-eight hours, U.S.-Israel relations went from "unbreakable," according to Vice President Joe Biden, to "perilous," as ascribed to an "unnamed senior U.S. official." This drastic mood swing risks overshadowing the great achievement of the vice president's Middle East trip -- the affirmation for Israelis (as well as those Arabs and Iranians following his words) that the Obama administration is "determined to prevent Iran from acquiring nuclear weapons."

ContextThe central purpose of the Biden visit was to cap a months-long "reset" of U.S.-Israel relations within a larger reorientation of U.S. Middle East policy.

When the new administration came to office, its Middle East policy was motivated by three principles:

that Israeli-Palestinian peacemaking...