In tough language rare for an Israeli diplomat in Washington, Israeli ambassador to the US Ron Dermer said Tuesday that Israel was “deeply disappointed” in the State Department’s decision to continue dealing with the Palestinian Authority now that it has Hamas support.

“Israel is deeply disappointed with the State Department’s comments today on the Palestinian unity government with Hamas, a terrorist organization responsible for the murder of many hundreds of Israelis, which has fired thousands of rockets at Israeli cities, and which remains committed to Israel’s destruction,” Dermer wrote in a Facebook post.

“This Palestinian unity government is a government of technocrats backed by terrorists, and should be treated as such,” he said. “With suits in the front office and terrorists in the back office, it should not be business as usual.”

Israeli envoys rarely publicly rebuke US administrations. Dermer’s was the first public comment on the matter that was not anonymous.

In the first remark by an Israeli cabinet member on the growing friction between Israel and the US, Communications and Home Front Defense Minister Gilad Erdan (Likud) said early Tuesday that, in backing the new Palestinian leadership, “American naivete reached new heights.”

“Cooperation with Hamas, designated in the US as a terror group that murders women and children, is unfathomable,” he added.

On Monday, Israel’s ambassador to the UN, Ron Prosor, said that commending the Fatah-Hamas partnership is “lending legitimacy to terror attacks against Israel.”

Ron Prosor, permanent representative of Israel to the UN, addresses the Security Council on October 22, 2013, at UN headquarters in New York. (photo credit: United Nations)

Ron Prosor, permanent representative of Israel to the UN, addresses the Security Council on October 22, 2013, at UN headquarters in New York. (photo credit: United Nations)

In a letter to the president of the UN Security Council, Prosor wrote that Hamas “may seek the veneer of legitimacy by partnering with the Palestinian Authority but it is clear that the terrorist group remains committed to destroying Israel.”

Prosor added that the international community must condemn terrorist attacks against Israel.

Earlier Monday, Israeli government officials in Jerusalem slammed the United States for announcing that it will work with the new Palestinian unity government, sworn in earlier Monday. In strikingly bitter comments, officials said that rather than cooperating with a government backed by a terror group, Washington ought to be urging Palestinian Authority President Mahmoud Abbas to disband his pact with Hamas and resume peace negotiations with Israel.

“We are deeply disappointed by the comments of the State Department regarding working with the Palestinian unity government. This Palestinian government is a government backed by Hamas, which is a terror organization committed to Israel’s destruction,” Israeli government officials said. “If the US administration wanted to advance peace, it should be calling on Abbas to end his pact with Hamas and return to peace talks with Israel,” they added. “Instead, it is enabling Abbas to believe that it is acceptable to form a government with a terrorist organization.”

Prime Minister Benjamin Netanyahu’s office and the Foreign Ministry in Jerusalem declined to comment on the record. Earlier Monday, Israel’s senior ministers decided to boycott the new government, since it is backed by Hamas, designated a terrorist organization by Israel and the US.

In a decision approved at a special meeting of the Ministerial Committee for National Security Affairs, Netanyahu and eight top ministers said they would not deal with the new government and would form a team to “examine courses of action” in light of the new Palestinian unity government.

State Department spokeswoman Jen Psaki said the US believes Abbas has “formed an interim technocratic government…that does not include members affiliated with Hamas.” Therefore, she added, “With what we know now, we will work with this government.”

Psaki did say, however, that Washington “will continue to evaluate the composition and policies of the new government and if needed we’ll modify our approach.” She later added that the administration would be “watching carefully to make sure” that the unity government upholds the principles that serve as preconditions for continuing US aid to the PA.

Psaki’s announcement was a major surprise to Israeli leaders; sources in Washington had been quoted in Israel in recent days saying the US would not immediately recognize the new PA government.

As recently as Sunday, Secretary of State John Kerry called Abbas and “expressed concern about Hamas’s role in any such government and the importance that the new government commit to the principles of nonviolence, recognition of the state of Israel and acceptance of previous agreements with it,” Psaki had said.

Earlier Monday, Kerry discussed the recent developments in a phone call with Netanyahu. State Department officials would not discuss the content of the conversation, or comment on whether the US administration’s announcement had come as a surprise to the Israeli government.

Asked if Israel would agree to return to the negotiating table after it suspended the talks in April, she said that would be up to the Israeli government to decide.

“It is ultimately up to the parties … to make the difficult decisions about coming to the negotiating table,” Psaki said. “So we will see. We are not in a position to make a prediction at this point.”

Psaki said that the United States is open to the current plan set out by the interim PA unity government, according to which long-delayed elections in the Palestinian Authority will be held in six months’ time.

“As a matter of principle we support democratic free and fair elections,” Psaki said, but added that “it is too early to speculate as to what the outcome will be and we will let events proceed.”

The State Department spokeswoman commented that although the US continues to expect Abbas to uphold his commitment to maintaining security coordination with Israel, Hamas’s support for the current government did not change the American perspective on culpability for rocket attacks launched toward Israeli targets from the Hamas-controlled Gaza Strip.

“We expect the PA to do everything in its power to prevent attacks from Gaza, but we understand that [the] Gaza Strip is under the control of Hamas,” Psaki explained.

In Ramallah on Monday, Abbas swore in 17 ministers in a new technocratic government meant to steer the PA toward elections within six months.

Abbas swore in the ministers Monday afternoon after Gaza’s Hamas rulers and Abbas’s Fatah resolved a last-minute disagreement over a key government ministry.

He hailed the “end” of Palestinian division, saying: “Today, with the formation of a national consensus government, we announce the end of a Palestinian division that has greatly damaged our national case.”

Abbas has pledged that the new administration will abide by the principles laid down by the Middle East peace Quartet that call for recognizing Israel, rejecting violence and abiding by all existing agreements, though Hamas has yet to ratify those conditions.

JTA, AFP, Elhanan Miller and Times of Israel staff contributed to this report.