Senior Fatah official Azzam Al-Ahmed, left, head of the Hamas government Ismail Haniyeh and senior Hamas leader Moussa Abu Marzouq hold hands after announcing a reconciliation agreement in Gaza City on April 23. (Suhaib Salem/Reuters)

Israel broke off peace talks with the Palestinians on Thursday, saying that a planned reconciliation between the moderate faction participating in the talks and the militant Islamist group Hamas made negotiation impossible.

The rupture appeared to be the final blow to an ambitious U.S.-sponsored effort to frame a peace treaty this year. Israeli-Palestinian talks that began last summer under heavy American pressure were already sputtering and were due to expire next week.

The negotiations, always a long shot, marked the first deep involvement by the Obama administration to address the in­trac­table conflict. The direct Israeli-­Palestinian talks, often with a U.S. mediator present, had been the most sustained and substantive such discussions in more than five years.

Palestinian leaders said the proposed unified government should not be a bar to further talks with Israel, and Washington insisted Thursday that the troubled peace effort is not dead. But Israeli Prime Minister Benjamin Netanyahu appeared to rule out all discussion with a Palestinian government that includes Hamas in any capacity.

“I think the pact with Hamas kills peace,” Netanyahu said in an interview with NBC. “If it moves forward, it means peace moves backward.”

The Iranian-backed Hamas does not recognize Israel as a legitimate country, and Israel accuses the group of harboring extremists who carry out attacks on Israel from inside the Gaza Strip, a territory that Hamas rules.

The moderate Fatah party had announced Wednesday that it will reunite with Hamas, ending a seven-year split. An agreement signed in Gaza gives Palestinian Authority President Mahmoud Abbas five weeks to form a unified government.

It was not clear how Hamas would be integrated into the Fatah leadership, or whether the deal will hold. Secretary of State John F. Kerry spoke to Abbas on Thursday, after a call with Netanyahu on Wednesday. The State Department gave few details, but it said Kerry expressed disapproval of the reconciliation plan.

“We will never give up our hope or our commitment for the possibilities for peace,” Kerry said in brief remarks at the State Department. “We believe it is the only way to go. But right now, obviously, it’s at a very difficult point and the leaders themselves have to make decisions. It’s up to them.”

After a meeting of Netanyahu’s security cabinet, Israel announced Thursday that it will suspend peace talks with Abbas’s envoys at least during that five-week period. After that, the Netanyahu government said, it will refuse to return to talks with any Palestinian government “backed by Hamas.”

“Whoever chooses the terrorism of Hamas does not want peace,” Netanyahu said in a statement issued shortly after the meeting.

Hanan Ashrawi, a member of the Palestine Liberation Organization’s Executive Committee, said the new government could be structured to preserve the mandate for peace talks, and she played down the effect of Hamas’s inclusion.

“The new government will adhere to the PLO political program and will not engage in negotiations or political decision-­making,” she said.

“The terms of the national reconciliation agreement are clear: Palestine honors its commitments, respects international law and continues its popular nonviolent resistance against the Israeli occupation.”

That appears to satisfy some but not all of the U.S. requirements for any future negotiations between the two sides. State Department spokeswoman Jen Psaki listed the criteria Thursday: “commitment to nonviolence, recognition of the state of Israel and acceptance of previous agreements and obligations.”

The United Nations’ envoy for the Middle East peace process, Robert Serry, met with Abbas on Thursday and issued a statement afterward saying that the Palestinian leader had assured him that the new government will comply with PLO commitments, including “recognition of Israel, nonviolence and adherence to previous agreements.”

The United Nations supports a unified Palestinian government, Serry said, “as the only way to reunite the West Bank and Gaza under one legitimate Palestinian Authority.”

To keep the talks alive, both sides would have to agree to extend the discussions past an April 29 deadline that Kerry set when formal negotiations began last year or resume them after a hiatus. The nine-month deadline was supposed to keep both sides at the table and focused on the most difficult issues.

Kerry had already acknowledged that it would slip, and the goal before this week’s events had been to find ways to offer each side sweeteners that could keep them at the table.

“There is always a way forward,” he said Thursday.

Without compromises from the leaders, however, peace “becomes very elusive,” Kerry said.

His chief negotiator, former ambassador to Israel Martin Indyk, will remain in the region for now.

Kerry has long said that the talks may represent the last real chance to create an independent Palestine alongside Israel. Israeli settlement-building on land that the Palestinians claim for a state is one major obstacle. The hardened anger and grievance of both sides is another. The longer the conflict runs, the larger and more immutable those obstacles become.

Netanyahu’s coalition government includes members opposed to the peace talks but none who advocate armed conflict against the Palestinians.

If Abbas had hoped that reconciliation with Hamas would give him leverage to demand greater concessions from Israel, he apparently miscalculated: The move either forced or allowed Netanyahu to walk away.

In addition to halting the talks indefinitely, the Israeli government said it is considering imposing economic sanctions against the Palestinian Authority as a way to punish Abbas.

Israel took similar steps last month after the Palestinians approached 15 international organizations to gain formal recognition as a state. Israel was angered by that move but did not cancel talks. The Hamas deal, however, made it impossible to continue, Israeli officials said.

“Abbas has formed an alliance with a murderous terrorist organization that calls consistently for Israel’s destruction,” Netanyahu said in a statement issued shortly after the vote. “Instead of choosing peace, he has formed an alliance with an organization whose charter calls on Muslims to fight and kill Jews.”

Eglash reported from Jerusalem.