I’ve grown so pessimistic about Israel-Palestine that I find myself agreeing with Israel’s hard-line foreign minister, Avigdor Lieberman: “Anyone who says that within the next few years an agreement can be reached ending the conflict simply doesn’t understand the situation and spreads delusions.”

That’s the lesson of early Obama. The president tried to rekindle peace talks by confronting Israel on settlements, coaxing Palestinians to resume negotiations, and reaching out to the Muslim world. The effort has failed.

It has alienated Israel, where Obama is unpopular, and brought the president of the Palestinian Authority, Mahmoud Abbas, close to resignation. It’s time to think again.

What’s gone wrong? There have been tactical mistakes, including a clumsy U.S. wobble toward accepting Israeli “restraint” on settlements rather than cessation. But the deeper error was strategic: Obama’s assumption that he could resume where Clinton left off in 2000 and pursue the land-for-peace idea at the heart of the two-state solution.

This approach ignored the deep scars inflicted in the past decade: the killing of 992 Israelis and 3,399 Palestinians between the outbreak of the Second Intifada in 2000 and 2006; the Israeli Army’s harsh reoccupation of most of the West Bank; Hamas’ violent rise to power in Gaza and the accompanying resurgence of annihilationist ideology; the spectacular spread of Jewish settlements in the West Bank; and the Israeli construction of over 250 miles of a separation barrier that has protected Israel from suicide bombers even as it has shattered Palestinian lives, grabbed land and become, in the words of Michael Sfard, an Israeli lawyer, “an integral part of the West Bank settlement plan.”

These are not small developments. They have changed the physical appearance of the Middle East. More important, they have transformed the psychologies of the protagonists. Israelis have walled themselves off from Palestinians. They are less interested than ever in a deal with people they hardly see.

As Ron Nachman, the founder of the sprawling Ariel settlement, comments in René Backmann’s superb new book, “A Wall in Palestine,” the wave of Palestinian suicide attacks before work on the barrier began in mid-2002 meant that: “Israelis wanted separation. They did not want to be mixed with the Arabs. They didn’t even want to see them. This may be seen as racist, but that’s how it is.”

And that’s about where we are.

With Palestinians saying, “Not one inch further will we cede.” The myriad humiliations of the looping barrier, which divides Palestinians from one another as well as from Israel, have cemented this “Nyet.”

On the surface, Obama’s decision to tackle settlements first was logical enough. Nothing has riled Palestinians as much as the continued flow of Israeli settlers into East Jerusalem and the West Bank. Both Oslo (1993) and the Road Map (2003) called for settlements to stop, but the number of settlers has risen steadily to over 450,000.

The president was categorical in his Cairo speech: “The United States does not accept the legitimacy of continued Israeli settlements.”

Nor do I. But facts are hard — and Obama has tried to ignore them. The history briefly outlined above makes clear that the right-wing government of Prime Minister Benjamin Netanyahu won’t deviate from the pattern of settlement growth established since 1967.

Indeed, Backmann’s book (from which the Sfard quote is also taken), demonstrates a relentless continuity of Israeli purpose, now cemented by a fence whose aim was in fact double: to stop terrorists but also “to protect the settlements, to give them room to develop.”

That is why, even at 250 miles, the barrier (projected to stretch over 400 miles) is already much longer than the pre-1967 border or Green Line: It burrows into the West Bank to place major settlements on the Israeli side, effectively annexing over 12 percent of the land.

The United States condoned the construction of this settlement-reinforcing barrier. It cannot be unmade — not for the foreseeable future. Peace and walls do not go together. But a truce and walls just may. And that, I must reluctantly conclude, is the best that can be hoped for.

Obama, who has his Nobel already, should ratchet expectations downward. Stop talking about peace. Banish the word. Start talking about détente. That’s what Lieberman wants; that’s what Hamas says it wants; that’s the end point of Netanyahu’s evasions.

It’s not what Abbas wants but he’s powerless. Shlomo Avineri, a political scientist, told me, “A nonviolent status quo is far from satisfactory but it’s not bad. Cyprus is not bad.”

I recall my friend Shlomo dreaming of peace. That’s over. The last decade destroyed the last illusions: hence the fence. The courageous have departed the Middle East. A peace of the brave must yield to a truce of the mediocre — at best.

At least until Intifada-traumatized Israeli psychology shifts. I agree with the Israeli author David Grossman when he writes: “We have dozens of atomic bombs, tanks and planes. We confront people possessing none of these arms. And yet, in our minds, we remain victims. This inability to perceive ourselves in relation to others is our principal weakness.”