As President Obama enters the re-election campaign in earnest this fall, he’ll face a huge problem, largely of his own making: a growing expectation that, by September, the United Nations will declare a Palestinian state without Israel’s consent.

President Shimon Peres visited Washington this week to devise strategy with Obama in an attempt to avert this looming diplomatic train wreck. By now, American diplomats well understand the dangers in Palestinian Authority President Mahmoud Abbas’ strategy of bypassing negotiations with Jerusalem and enlisting an automatic UN majority to declare a Palestinian state, instead.

“Be careful,” Peres warned Security Council ambassadors and envoys of several Arab states yesterday. Speaking during breakfast at the Midtown offices of the International Peace Institute, Peres asked the diplomats what would happen the morning after the General Assembly recognized the state of Palestine: “Can the UN provide a guarantee that there won’t be missiles, [that] there won’t be terror?”

As Peres spoke, an aide slipped him a note, informing him that a missile from Gaza had just hit a school bus in southern Israel, seriously injuring a 16-year-old boy. Would the Palestinian state in the West Bank resemble Gaza after every Israeli soldier and settler left it in 2005? Peres asked.

Abbas claims that the only item that needs to be finished on the way to statehood is for Israel to leave and delineate a border based on the 1949 armistice line. Yet every document the Palestinians have signed with Israel since the 1993 Oslo Accords clearly states that declaring a state requires the agreement of both sides.

To reach an agreement with Israel, Abbas would need to sign security arrangements, make concessions in Jerusalem and give up the Palestinian demand to flood Israel with Arab “refugees.”

Abbas, however, is politically weak, and making such concessions would spell his doom. So, instead, he relies on a plan devised two years ago by his prime minister, Salem Fayyed, to declare a state in 2011 regardless of any progress in talks with Israel.

That plan received its most significant boost last September when Obama addressed the UN General Assembly, expressing his hope that “when we come back here next year, we can have an agreement that will lead to a new member of the United Nations — an independent, sovereign state of Palestine, living in peace with Israel.”

That florid piece of rhetoric was dependent much more on “Obama magic” than on a diplomatic breakthrough. Nevertheless, Obama’s listeners saw in it an American IOU. The parts about “agreement” and “peace with Israel” were quickly forgotten. By now, all that diplomats in Arab capitals (and everywhere else, including Europe) remember is a due date for Palestine to become a UN member.

Even Obama’s own team now recognizes this as a trap. As UN Ambassador Susan Rice told Congress this week, “You can pass a resolution, but that does not a viable state create.” A viable Palestinian state “can only be established through direct negotiations between the parties,” she said.

Only the Security Council can admit members to the UN, and only Washington can stop such a move, using our veto right. As he enters next year’s campaign this fall, Obama knows that other presidential hopefuls will attack his commitment to Israel, which most Americans still support over its enemies. Failing to wield a UN veto would cost Obama dearly politically.

On the other hand, some Obama aides and supporters in the media think that blocking a Security Council Palestinian-state resolution is bound to stir Arab passions and erode American credibility — just as we are trying our hardest to navigate a fast-changing Mideast.

As Peres said yesterday, pro-democracy forces in the region would get a boost “if we shall relieve them of the Israeli-Arab conflict.” But Abbas’ plan to bypass negotiations and go to the UN, instead, will surely exacerbate the conflict — and therefore give excuses to new (or old) tyrants to turn away from the changes necessary to bring the Arabs into the 21st century.

Obama has long believed — wrongly — that ending Arab-Israeli enmity is central to resolving the Mideast’s problems. Perhaps he still does. Yet, more than on any other issue, this is where he keeps shooting himself in the foot. Long after last year’s UN applause has died, he now needs to diffuse a diplomatic landmine.

Obama now must make clear that an American veto is coming. He then should reprioritize his Mideast agenda — and perhaps thank good old Peres for allowing his rescue. beavni@gmail.com