Eager to head off a diplomatic crisis with its most important peace partner, Israel apologized to Egypt on Saturday over the deaths of three Egyptian soldiers who were accidentally killed last week during an Israeli military incursion into the Sinai peninsula.

But even if a deeper fracture was averted by the rare expression of regret, a spat that saw Egypt threaten to recall its ambassador is another sign of the rising ill will between the two key U.S. allies. The episode also reflects how pro-democracy rebellions spreading across the Arab world are creating new realities in the decades-old Mideast conflict.

In Egypt, public opinion has sharpened Cairo's criticism of Israel since the revolution that swept President Hosni Mubarak from power in February. That's forcing Israel to recalibrate long-held policies and assumptions about its security, with some critics complaining that Prime Minister Benjamin Netanyahu's coalition government has been slow to comprehend the changes sweeping the region.

Israeli government officials acknowledged that the old rules in dealing with Egypt may no longer apply to the interim government in Cairo.

"This is probably what the new Egyptian government is going to look like," said one Israeli government official, speaking on the condition of anonymity. "They have to follow the beat of the street. For Israel, that means more tumultuous times."

U.S. officials were in contact with both sides Saturday in an effort to smooth the conflict, which comes at a difficult time for the Obama administration. Relations with the Egyptian government have been strained recently over what the United States has deplored as creeping anti-Americanism, and the White House has clashed repeatedly with the Netanyahu government.

Mubarak kept a cool peace with Israel, muting anti-Israeli sentiment for strategic goals that included combating Islamic extremism and keeping close ties with Washington. But Egypt's new ruling military council is sensitive to public opinion and firmly voices its displeasure with Netanyahu's government.

"The political equation between Egypt and Israel has changed because the voice of the Egyptian people is being heard," said Wahid Abdel Maguid, an analyst at Al Ahram Center for Political and Strategic Studies in Cairo. "This strengthens Egypt's hand."

The latest test of the landmark 1979 Egyptian-Israeli peace accord came Thursday, when gunmen killed six civilians and two Israeli soldiers in southern Israel. Israeli forces chased the militants across the border into Egypt, where the Egyptian soldiers were killed, apparently in assaults by Israeli helicopters. Israel says the attackers originally came from the Gaza Strip and infiltrated Israel through the Sinai desert.

Egypt's abrupt threat Saturday to recall its ambassador to Israel unless it received an apology startled Israeli officials, who noted that a formal investigation had not yet even confirmed that Israel's military was responsible for the Egyptian deaths. Netanyahu huddled in emergency meetings Saturday to formulate a response.

The Sinai incident highlights the Islamist passions and volatile politics facing Egypt's generals and their appointed interim government. Islamist groups, which are expected to do well in this fall's parliamentary elections, are stoking anger in the street and forcing the generals to placate the public mood while not jeopardizing ties to Israel.

Any threat to the 1979 peace accord would draw pressure from the U.S., which gives the Egyptian military more than $1 billion a year. But the atmosphere is increasingly acrimonious. Egyptian Prime Minister Essam Sharaf and his Cabinet condemned Israel's use of force in language more stinging than Mubarak would have permitted.

"Both parties can't afford to escalate tensions any further," said Nabil Abdel Fattah, a political analyst. He added that the current unrest in Libya, Syria, Yemen and other Arab countries was too dangerous to be compounded by deteriorating relations between Egypt and Israel.

The most recent recriminations come three months after Cairo angered Israel by opening the Rafah border crossing to Gaza and improving ties with the militant Palestinian group Hamas, which rules the coastal territory.

Lawlessness in the Sinai threatens Israel's security and reveals a lack of vigilance by Egypt to crush arms smugglers, criminal Bedouin tribes and Islamic militants, all of whom have become more brazen since Mubarak's downfall. The Egyptian army sent more than 1,000 soldiers into the Sinai last week and arrested nearly 20 extremists. But a day later, gunmen along the border killed the eight Israelis.

People in Israel have been watching events across the border with Egypt with growing unease. Many Israelis were sorry to see Mubarak deposed and have expressed disapproval of the public trial of the former leader, whom many Israelis credit with maintaining the Egyptian-Israeli peace accord.

Yet until recently, many Israeli analysts and government officials had expressed confidence that the interim Egyptian government would never do anything to endanger relations. Now some of those calculations have been called into question.

The deterioration in relations with Egypt comes as Israel is looking increasingly isolated in the region. Turkey, a onetime close ally, is refusing to restore diplomatic ties until Israel apologizes for the deaths last year of nine Turkish activists, who were shot by Israeli commandos as they tried to break a naval blockade of Gaza. Jordan's king has voiced growing frustration over the lack of Israeli-Palestinian peace talks and Israel's continued West Bank settlement construction.

Without Egypt's political and military cooperation, Israel's security strategy will have to change dramatically, experts say. Since the 1979 treaty, Israel has not had to worry as much about protecting its southwestern border from attack. Mubarak's support also gave Israel almost free rein in cordoning off Gaza.

Now the potential price of military actions in Gaza or against militant factions in the Sinai is higher for Israel because it will also need to gauge the effect on its relations with Egypt.

Separately Saturday, violence continued as Gaza militants fired about 20 rockets into southern Israeli towns, killing one person and wounding about two dozen others, including three Palestinian industrial workers. For the first time since the recent violence began, Hamas joined other militant factions in firing rockets against Israel.

Israel continued its airstrikes against Gaza targets, saying it had hit two smuggling tunnels, a weapons depot and a squad of militants about to fire a rocket. Palestinians said three civilians were killed in one of the strikes, bringing the death toll in Gaza since Thursday to 14.