ICC prosecutor Fatou Bensouda has started a preliminary investigation into possible war crimes in the Palestinian territories. (Peter Dejong / POOL/EPA)

— Following a decision by prosecutors at the International Criminal Court on Friday to launch an inquiry into possible war crimes in the Palestinian territories, the ­longest-running conflict in the Middle East enters a volatile new stage.

No one — not the Americans, Israelis or Palestinians — can predict with any certainty what will happen next, though they warn that the already crumbling relationship between Israel and the Palestinian Authority is likely to get worse.

If civil and security cooperation between Israel and the West Bank ends because of rancor over the ICC probe, Israeli soldiers could return to the streets of Ramallah as the Palestinian administration collapses.

Nor does anyone know exactly what ICC prosecutor Fatou Bensouda will examine in the coming months. The high number of civilian deaths in Gaza during the summer war? Indiscriminate Hamas rocket fire at Israeli towns? Her announcement of a preliminary examination refers only to “the situation in Palestine.” The inquiry will focus on the nature of possible crimes, the admissability of evidence and whether the court has jurisdiction.

The international court has never handled a case as legally complex and as politically loaded as the one that could arise from the Israeli-Palestinian conflict.

For example, Palestine is not a state, according to the Obama administration, which argues the Palestinians do not have standing. Further complicating matters, one of the Palestinian governing partners is Hamas, designated a terrorist organization by the United States and several other nations.

The Israeli military, too, is conducting its own investigations into the Gaza war, which could produce charges against commanders, undercutting the need for an ICC investigation.

Any possible criminal charges against Israelis or Palestinians would likely take years to adjudicate. There is no timeline or statute of limitations. The ICC prosecutor has nine open examinations into alleged war crimes in countries such as Ukraine, Afghanistan and Colombia that have been grinding along for seven or eight years without a resolution.

Only after a preliminary exam is complete do judges on the court make a ruling to open a full investigation. After that, they may or may not issue charges and conduct a trial.

Israeli leaders blasted the decision by ICC prosecutors to open a probe. Prime Minister Benjamin Netanyahu vowed Sunday that Israeli soldiers would never be tried by the ICC and excoriated the court for giving “international cover to international terror.”

Israeli Intelligence Minister Yuval Steinitz called the ICC “a kangaroo court.”

Netanyahu mocked the ICC prosecutor’s decision to open the case. “I won’t be surprised if ISIS, al-Qaeda and Hezbollah follow suit,” he said. “See, Hamas has already announced that they will join their Palestinian partner, President Abbas, in filing complaints against Israel as a result of this decision. To what depths of absurdity has the ICC sunk?”

Israel promised to take retaliatory measures. Israel has already withheld transfer of the monthly customs duties it collects for Palestinian imports — $125 million that the Palestinian Authority uses to pay salaries.

The Palestinian administration in Ramallah announced Sunday that it would pay its 160,000 civil servants only 60 percent of their December salaries, according to a report by the Maan news agency. Palestinians officials say that if Israel withholds tax monies month after month, the Palestinian Authority will collapse, and Israel will have to take over civil and security duties in the occupied territories.

The Obama administration has warned that the Palestinian move at the ICC will escalate tensions. It condemned the decision by ICC prosecutors to move forward.

“As we have said repeatedly, we do not believe that Palestine is a state, and therefore we do not believe that it is eligible to join the ICC,” State Department spokesman Jeff Rathke said Friday. “It is a tragic irony that Israel, which has withstood thousands of terrorist rockets fired at its civilians and its neighborhoods, is now being scrutinized by the ICC.”

The Palestinians are watching warily to see what Washington does. Congress could cut funding for $400 million in annual U.S. aid projects, which provide tens of thousands of jobs in the West Bank.

Sen. John McCain (R-Ariz.), the new chairman of the Senate Armed Services Committee, arrived with a bipartisan delegation in Israel on Sunday.

The Palestinian Authority applauded the ICC decision to begin its probe. Frustrated by the failure of U.S.-brokered peace talks and under growing pressure from his people to confront the Israeli occupation, Palestinian President Mahmoud Abbas is now waging diplomatic war against Israel, betting on a risky campaign to fully “internationalize the struggle” by moving toward the international court in The Hague and away from the United States.

“The ICC is a wake-up call to every Israeli,” said Mohammad Shtayyeh, a veteran Palestinian peace negotiator who resigned in protest halfway though the last round of talks, which collapsed in April.

Shtayyeh said the Palestinians want to isolate, sanction and anger Israel and force Israelis to return to the negotiating table with an acceptable peace deal.

In recent months, U.S. and European diplomats have been working to cool heated rhetoric between Israel and the Palestinians, seeking “a freeze for a freeze” out of concern that if the sides do not calm down, they could tear each other apart.

Those efforts appear to have failed.

On Sunday, protesters from Abbas’s Fatah party threw shoes and eggs at Canadian Foreign Minister John Baird during his visit to Ramallah. Canada opposed a pro-Palestinian resolution introduced in the U.N. Security Council last month that sought to end the Israeli occupation and create a Palestinian state.

Canada and the United States say the creation of a sovereign Palestinian state, which they support, can only be accomplished through direct negotiations with Israel, not by U.N. declarations.

Israel and its supporters say that any move against Israel at the ICC would likely be answered by calls to prosecute Islamist militants in Hamas who control the Gaza Strip.

“What Hamas is doing is a classic example of what you need the ICC for,” said Dore Gold, president of the Jerusalem Center for Public Affairs and a former Israeli ambassador to the United Nations.

He warned, “If Abbas wants to launch a whole new wave of ‘lawfare,’ then he is highly exposed as a person and as a Palestinian leader. Does he really want to go down that route with the state of Israel?”

Hamas did not seem too worried.

“The step is a gleam of hope for the Palestinian people, a chance of seeing enemy leaders brought to justice and punished for their crimes,” Hamas spokesman Fawzi Barhoum said Saturday.