WASHINGTON — President Obama’s relentless push for some sort of first-stage Mideast peace deal by the end of this month was dealt a strong blow by Fatah and Hamas deciding to put aside their differences and unite.

Hamas’ information office said the pact between Palestinian Authority President Mahmoud Abbas and Hamas political bureau leader Khaled Mashal was simply implementing the previous unity agreements signed years ago in Doha and Cairo — pacts followed by years of vicious fighting between the parties.

Abbas agreed to “start talks on forming the new transitional national unity government that will be formed within five weeks, and will be holding talks on declaring new elections that would be held at least six months after the new government is formed,” according to Hamas’ Ezzedeen Al-Qasam Brigades.

Israeli Foreign Minister Avigdor Lieberman declared this move “tantamount to a signature on the conclusion of negotiations between Israel and the Palestinian Authority.”

“It is impossible to make peace with Israel as well as with Hamas, a terrorist organization advocating for Israel’s destruction,” Lieberman said.

State Department press secretary Jen Psaki admitted to reporters at Wednesday’s briefing that the “timing” of the agreement was “troubling,” and at today’s briefing a journalist commented that Obama and Secretary of State John Kerry “have managed to pull off the full Quixote here, or rather a double-Quixote, that is not only having tilted at the windmills, but having lost.”

Psaki placed the blame at the feet of both the Israelis and the Palestinians, noting that “if we look back at the last several months, over the course of nine months even, there are unhelpful steps that have been taken by both parties.”

“There have been ups and downs in the process throughout. And still, this process needs to work its way through,” she said.

She said Kerry called Abbas this morning. “The secretary noted that he was disappointed by the reconciliation announcement and repeated the elements that any Palestinian government would need to have, the same principles that President Abbas has long supported. President Abbas, again, they decided they would remain in touch,” she continued.

“Of course, the principles — just to reiterate what I said yesterday, but for those of you who weren’t here, the three principles are, of course, commitment to nonviolence, recognition of the state of Israel, and acceptance of previous agreements and obligations between the parties,” Psaki added. “They also discussed efforts underway, those efforts that have been underway between Israelis and Palestinians to extend the negotiations. I also just wanted to reiterate that we view it as essential that both parties exercise, all sides exercise maximum restraint and avoid escalatory steps.”

Psaki said Kerry bent Abbas’ ear about “the benefits of… a final status agreement.” She said he’d be having the same conversation with Israeli Prime Minister Benjamin Netanyahu.

When asked if Abbas told Kerry why he felt the need to power-share with Hamas now, Psaki replied, “That’s not a part of the conversation I’m going to read out.”

As the administration tried to keep the hope of a road map alive, Netanyahu made clear that “whoever chooses the terrorism of Hamas does not want peace.”

“Abu Mazen has formed an alliance with an organization whose covenant calls for Muslims to fight and kill Jews. Hamas has fired more than 10,000 missiles and rockets at Israeli territory and has not halted terrorist actions against Israel even for a minute,” Netanyahu said after the Israeli cabinet unanimously agreed to not negotiate with a Hamas-backed government and to respond to the provocation with “a series of measures.”

“The agreement between Abu Mazen and Hamas was signed even as Israel is making efforts to advance the negotiations with the Palestinians. It is the direct continuation of the Palestinians’ refusal to advance the negotiations,” the prime minister continued. “Only last month Abu Mazen rejected the framework principles proposed by the United States. Abu Mazen has refused to even discuss recognizing Israel as the national state of the Jewish People. He violated existing agreements by unilaterally applying to accede to international treaties and then formed an alliance with Hamas.”

Netanyahu told MSNBC today that Abbas’ decision was “a giant leap backward.”

He called Fatah’s pledge that they would continue to comprise the majority of the government “the oldest trick in the book… the ‘front office/back office gambit.’”