On his first—and probably last—major trip to the Middle East, President Bush has a final chance to reorient and reinvigorate U.S. diplomacy in the region. If the past is any guide, however, Bush will miss another opportunity to reach out to U.S. adversaries and diminish their motivation to play the spoiler.

U.S. strategy has sought to bolster so-called moderates—Israel, parts of Palestine, Lebanon and Iraq, Egypt, Jordan and the Arab states of the Persian Gulf—against so-called radicals:­ Hamas, Hizballah, Syria and Iran. The strategy has made a fractured region even more divided and led worried U.S. allies to hedge their bets.

Thus Qatar invited Iranian President Mahmoud Ahmadinejad to a summit of the Gulf Arab nations last month and Saudi Arabia hosted Ahmadinejad at the hajj—all at a time when the United States was seeking to isolate Iran over its nuclear program and support for Arab militants. Egypt, the second-largest recipient of U.S. aid after Israel, recently held talks with Iran about restoring formal diplomatic relations. Iraq’s Shi‘a government, perhaps fearful of antagonizing Iran, refused a U.S. invitation to attend the Arab-Israeli peace summit in Annapolis in November. Syria did show up, only to remind Washington that no comprehensive peace can be achieved without resolving Syrian concerns.

Annapolis ended with a promise of robust diplomacy but Palestinian-Israel talks have already bogged down over Palestinian complaints about Israel’s continued expansion of settlements in East Jerusalem and Israeli anger at militant violence in both the West Bank and the Hamas-controlled Gaza Strip. In Lebanon, Hizballah leader Hassan Nasrallah has said he will continue to block selection of a new president—Lebanon has been without one since November 23—unless the Shi‘a-led opposition gets veto power in any future government. The one bright spot, ironically, is Iraq where Iran appears to have helped engineer a reduction of violence by pressuring Shi‘a hothead Moqtada Sadr to end attacks on other Shi‘a and on Americans. Iran, anticipating the end of the U.S. surge, is seeking to consolidate power in Baghdad and the south for its Shi‘a proxies.

The relative lull in Iraq gives Bush an excuse to modify course on Iran, especially when combined with a new U.S. intelligence estimate that claims Iran ended a covert nuclear-weapons program in 2003. Growing instability in Afghanistan and another Iranian neighbor, Pakistan, provides another incentive to reach out to Tehran. Benazir Bhutto's assassination underlined that the biggest threat to U.S. interests and to the region remains suicidal Sunni fundamentalist terrorism, not the Tehran government which, the new intelligence estimate says, makes decisions logically according to a “cost-benefit analysis.”

Iran and the United States share concerns about a Pakistan in crisis. As the world's largest Shi‘a Muslim country, Iran worries that Sunni fundamentalists could come to power in Islamabad and increase discrimination against Pakistan's Shi‘a minority. An unraveling Pakistan would also exacerbate ethnic tensions along the border with Iran and increase trafficking in narcotic drugs.

Perhaps mindful of these common concerns, Iran’s supreme leader, Ayatollah Ali Khamenei, has for the first time opened the door to improving relations with the United

States. He told an audience in the central Iranian city of Yazd on Thursday that while re-establishing ties would be “harmful” now, “we never said this relationship should be cut forever . . . Certainly, the day when having relations with America is useful for the nation, I will be the first one to approve.”

Now is time for the Bush Administration to respond by replacing its divisive policies in the Middle East with a strategy of combine and conquer. At a minimum, the United States should offer to take part in a regional security conference that brings Iran to the table along with its U.S.-allied neighbors. A new security forum would provide a venue for discussing terrorist threats afflicting all these nations, an opportunity for direct U.S.-Iran dialogue and the place and political face Iran has been seeking for decades.