o much for the constructive mediator. In a costly blow yesterday to America's credibility as an honest broker for a Middle East peace, President Bush endorsed Israeli plans to retain some West Bank settlements and to essentially reject the Palestinians' "right of return."

It has long seemed inevitable that a lasting peace would allow Israelis to keep some of the large West Bank settlements contiguous to Jerusalem and would offer, at most, a very limited right of return for the Palestinians whose families fled at the dawn of a Jewish state. But by accepting Prime Minister Ariel Sharon's terms absent any negotiation between the parties, Mr. Bush is essentially supporting Israel's right to impose a settlement of its choice on the Palestinians.

Mr. Bush's drastic and unfortunate policy reversal was announced as a beaming Mr. Sharon stood next to him in the White House. Mr. Sharon was eager to secure American backing on these issues in exchange for his plan to withdraw from the Gaza Strip, a decision that has proved to be quite divisive within his Likud Party. Mr. Bush, the affable host, obliged, just as two days earlier he had seemed to oblige a different guest, President Hosni Mubarak of Egypt, at his Texas ranch. Then, as this page approvingly noted, Mr. Bush indicated that he was not prepared to approve Mr. Sharon's plans to declare unilaterally that Israel would keep its West Bank settlements on the Israeli side of the recently constructed security barrier.

Until now, the United States has insisted that boundary questions — which are central to any eventual two-state deal — had to be negotiated as a last step.

Mr. Bush's desire to give Mr. Sharon a prize for pledging to withdraw from Gaza will compromise any subsequent attempts by Washington to broker a lasting settlement, to put it mildly. Palestinians and moderate Arab nations — as well as the European allies, for that matter — are furious that Mr. Bush acceded to Mr. Sharon's demands.