Contrary to many claims, the ‘pro-Israel’ factor is not the dominant constraint on any US eff ort to impose a comprehensive peace settlement. Nor did the pro-Israel lobby play a decisive role in the failure to reach a comprehensive peace in the 1990s. Th e most signifi cant eff ect of the pro-Israel factor in the United States is to give Israel the benefi t of the doubt by putting the onus on the Arab side to demonstrate its sincerity concerning peace. When Arab leaders have done this, they have greatly reduced the lobby’s ability to constrain US diplomacy. However, the greatest constraint on America relates to the balance of interests between the United States and the parties to the confl ict themselves. For the parties the details of any agreement are of much greater importance than they are for the United States, hence they are willing to pay greater costs than the latter is willing to impose on any confrontation. Consequently, under most conceivable circumstances the United States cannot impose a comprehensive settlement.