Washington ? Alarmed by Israeli plans to build new housing units in settlements and dimming prospects for American peace efforts, the Obama administration on Friday put out a rare and harsh public rebuke of its main Mideast ally.

The White House said Israeli Prime Minister Benjamin Netanyahu’s settlement plans were “inconsistent” with commitments the Jewish state has made previously and harmful to U.S. attempts to lay the groundwork for a resumption in peace talks between Israel and the Palestinians.

“United States does not accept the legitimacy of continued settlement expansion and we urge that it stop,” White House spokesman Robert Gibbs said in a statement. “We are working to create a climate in which negotiations can take place, and such actions make it harder to create such a climate.”

Netanyahu’s aides, speaking on condition of anonymity Friday because the plans have not been formally announced, said any Israeli settlement freeze would not halt building the new units and or block completion of some 2,500 others currently under construction. They also said the freeze would not include east Jerusalem, which the Palestinians hope to make their future capital.

The unusually blunt White House criticism reflected the administration’s growing frustration with Netanyahu, whose decision would approve hundreds of new housing units in West Bank settlements before considering even a temporary freeze in construction, as President Barack Obama has requested.

The White House typically refrains from commenting on such moves until they are formally announced. But in this case, U.S. officials said they acted because Mideast peace envoy George Mitchell had already been briefed on the Israeli plans earlier in the week.

State Department spokesman Ian Kelly said Mitchell and the Israelis had been having “a very open dialogue” in “very intense discussions.” He would not elaborate.

But one U.S. official familiar with Mitchell’s Wednesday meeting in New York with Netanyahu envoy Yitzhak Molcho and Israeli Defense Ministry chief of staff Michael Herzog said the Israelis “told Mitchell they were going to do it and he told them they could expect a sharp response.”

The official, who spoke on condition of anonymity to discuss a sensitive diplomatic exchange, said the meeting had “not gone well.”

The official added that the White House statement was released before a formal Israeli announcement of Netanyahu’s plans because “we wanted to send a strong signal early on.”

Publicly, the State Department had described Mitchell’s discussion with the Israeli delegation — which came after his talks with Netanyahu a week earlier in London — as a “good meeting.”

The department said Mitchell would travel again to the Middle East next week to follow up. That trip is still on, officials said Friday.

“The process will continue,” said one. The official also noted that the statement was not entirely negative and expressed appreciation for “Israel’s stated intent to place limits on settlement activity.”

“We are working with all parties — Israelis, Palestinians, and Arab states — on the steps they must take to achieve that objective,” said Gibbs.