Watching the news from Lebanon, it's poignant to read the title of a new memoir by Jordan's former foreign minister, Marwan Muasher, "The Arab Center: The Promise of Moderation." The daily headlines tell us that centrist Arabs such as Muasher are becoming an endangered species.

The center is under siege in Lebanon and across the Middle East as the region becomes more polarized between Iranian-backed extremists and U.S.-backed forces. Iran's proxies strike at will: seizing control of Beirut neighborhoods in a naked show of defiance; lobbing missiles into Israel from Gaza to disrupt peace talks; creating havoc in southern Iraq and Baghdad.

And then, with the cunning that makes Iran such a difficult adversary, Tehran's friends retreat -- striking deals that tilt each time a bit more in favor of the radicals. It's a familiar pattern: Iran unsheathes the sword, bloodies the moderates enough to show its power and then puts the sword back in the sheath. Would that America were so deft in helping its friends.

Muasher's book raises what may be the most damning criticism of the Bush administration's Middle East policy -- that it has unwittingly undercut the very people the United States wanted most to help. In Iraq, Iran, Lebanon, Syria, Palestine and even Jordan, the moderate voices in the center are weaker now than they were when President Bush took office in 2001. The United States has exposed its allies to danger and has not had the diplomatic skills to create a stable new order.

"Years from now, when the history of the modern Middle East will be written, what will it be titled . . . 'The Center Could Not Hold' or 'A New Beginning'?" asks Muasher. That question is still in the balance, but the current evidence is discouraging.

Secretary of State Condoleezza Rice puts a hopeful gloss on this process of confrontation by seeing it as part of a "realignment" in the Middle East that is clarifying the choices between radicals and moderates. Certainly the Saudis, Egyptians and Jordanians now see, as never before, the threat posed by Iran and its proxies. They're trying to check Iranian power through regional groups to support Lebanon and Iraq.

But has this growing polarization produced positive changes in the region? Has it contained Iranian influence or checked Iranian meddling? The mess in Lebanon says no.

Odd as it sounds, I fear that the Bush administration is making the same mistake as hard-liners in the region. It doesn't know when to compromise. It accumulates lots of chips through its military power, but it never plays them at the bargaining table.

Bush could have had a broad dialogue with Iran about regional stability in 2003; nope, the administration wasn't ready. The U.S.-Iranian diplomatic option arose again in March 2006, when Iran's supreme leader, Ali Khamenei, offered to send his top adviser, Ali Larijani, to Baghdad for talks about stabilizing Iraq; nope, the administration got cold feet, even though it had invited just such an initiative. Meanwhile, Syria has been signaling for more than a year that it wants U.S. help in negotiating a peace deal with Israel; nope, the administration doesn't trust Syria. So it has fallen to the Israelis to take up the Syrian peace feelers the United States is afraid to touch.

And now Lebanon: For many months, it has been obvious that the political logjam in Beirut could not be broken without some creative American maneuvers. Lebanon needs a strong state, backed by a strong army, but the administration hasn't been able to close the deals -- as on a new Lebanese president -- that could begin to make this a reality.

Back to my friend Muasher, the Jordanian diplomat. The most moving part of his book is his description of becoming Jordan's first ambassador to Israel after the 1994 peace treaty. He didn't want to do it. It meant crossing a "psychological barrier" and exposing himself and his family to Arab scorn. But he wondered: "Would you be able to live with yourself, knowing that you chickened out of a difficult assignment, even this one?" So he went to Tel Aviv and transcended the taboo against dealing with the "other."

Americans will have to learn how to deal with the "other," too, if we are going to get out of the Middle East mess. Iran thinks it's on a roll now, and Tehran's allies are so cocky that it's too late for this administration to make much progress. It had its chances but let them slip. So it will fall to the next administration to relearn the delicate, sometimes devious, skills of diplomacy that can rebuild the Arab center.