Palestinian and Israeli casualties are mounting at a pace that could surpass any other Israeli conflict in nearly a decade, amid signs of a deepening military and political stalemate driven by diplomatic gridlock, Palestinian militant resilience and the absence of a clear Israeli exit strategy.

The rising death toll in the Gaza Strip conflict propelled U.S. and European diplomats huddled in Paris to call for an extension of a 12-hour humanitarian truce Saturday that had afforded both sides a brief respite from the nearly three-week-old conflict.

Late Saturday, Israel approved a 24-hour extension of the truce but said it would retaliate if Hamas prevented its forces from continuing to destroy tunnel networks through which the militants have attempted to infiltrate Israel. Hamas fighters, though, resumed firing rockets and mortar rounds into Israel.

Before the truce began Saturday morning, six Israeli soldiers were killed in battles across the Gaza Strip, Israel’s military said. Meanwhile, Palestinian deaths rose to more than 1,035 on Saturday, according to Gaza health officials, a dramatic increase since the beginning of the ground incursion. In Israel’s 2009 Gaza offensive, about 1,400 Palestinians were killed.

Increasingly, the conflict is becoming a war of attrition, military and intelligence analysts say, resembling Israel’s war with Lebanon more than its previous conflicts with Hamas in 2009 and 2012. In Lebanon, too, casualties on both sides were high. Hamas, like Lebanon’s Hezbollah movement, has shown a determination to confront Israel with well-trained fighters, clear combat strategies and rockets — as well as its tunnel networks, the destruction of which is Israel’s stated objective.

Now, Israel is confronting the same kinds of divisive questions it faced in Lebanon: What are its goals in Gaza? And how long does it intend to remain there to achieve them? The questions underscore the country’s dilemma, torn between wanting a durable cease-fire and wanting to destroy Hamas’s ability to torment Israelis.

“The more you drag on, the more you stay there, the more the exit strategy becomes a blur,” said Yossi Melman, an Israeli intelligence analyst. “We will be trapped there, and we will have more casualties. If we don’t have a clear vision of what we want to achieve, we unwittingly will find ourselves reoccupying Gaza again.”

Neither side, nor any of the diplomats seeking an end to the crisis, wants that. In Paris, envoys from Qatar, Turkey, France, Britain, Germany, Italy and the United States worked late into the night Saturday in an attempt to win an extension of the cease-fire, despite the reignited tensions.

They viewed a truce lasting several days — the goal of diplomatic efforts that fell short last week in Cairo — as a bridge to a sustainable cease-fire that would clear a path to addressing both sides’ demands. Israel wants to see Hamas demilitarized, while Hamas’s core demand is the lifting of Israel’s economic blockade of Gaza.

U.S. Secretary of State John F. Kerry met first with Turkish Foreign Minister Ahmet Davutoglu, one of two key go-betweens for the United States, which is barred from direct contacts with Hamas leaders. “Palestinians need to live with dignity, freedom, with goods that can come in and out, and they need a life that is free from the current restraints that they feel on a daily basis, and obviously free from violence,” Kerry told reporters a day after his efforts to install a week-long truce fell short.

Even that oblique reference to the Israeli grip on Hamas-ruled Gaza was unusual for the United States, Israel’s principal ally and international defender.

“At the same time, Israelis need to live free from rockets and the tunnels that threaten them,” Kerry said, adding, “Every conversation we had embraces a discussion about these competing interests that are real for both.

Graphic: See how many rockets Hamas has launched into Israel and how many targets Israel has struck in Gaza

Kerry met with the foreign minister of Qatar later in the day. Qatar is well placed as an intermediary, since the rich Persian Gulf state is presumed to fund Hamas, which seized control of Gaza in 2007, and hosts leader Khaled Meshal. Qatar is the likely source of funds to pay suspended salaries for government workers in Gaza, which cash-strapped Hamas has been unable to do.

As a diplomatic breakthrough was sought, Gazans seized advantage of the pause in fighting. In the three hardest-hit towns, residents rushed back to gather belongings and search for missing relatives after 24 hours of intense fighting and heavy bombing by Israel that left deep impact craters where apartment blocks once stood. Whole neighborhoods were transformed into acres of twisted metal and concrete dust. More than 100 bodies were pulled from the rubble.

In the Shijaiyah neighborhood, east of central Gaza City, three brothers stood at the edge of a deep crater left by a large Israeli bomb. The day before it was their four-story apartment house, home to 30 family members. “We have nothing left,” said one of the brothers, Said Helou, 32, a baker.

Yussif Abid al-Hamid, an emergency medical technician, said it would take more than 12 hours to dig the bodies out from the debris. “We need heavy equipment here,” he said. “We need earthmovers. We can’t dig with our bare hands.”

In southern Israel, where most of the Hamas rockets land, residents also welcomed the pause.

“All of a sudden you could hear the birds again,” said Adele Raemer, who lives in Kibbutz Nirim, nestled along the border.

In the nearby farming community of Netiv Ha’asara, Roni Keidar and her husband were making preparations for a mourning ceremony for one of their employees, a Thai worker killed Wednesday by a Hamas mortar lobbed from Gaza. He was the third civilian to be killed on the Israeli side.

“It’s been a dreadful week,” Keidar said.

Even as it faces diplomatic pressure to agree to a durable truce, Israel has given mixed signals about its exit strategy from Gaza. Some Israeli military officials say they have a limited goal: to destroy Hamas’s vast tunnel network, which could take days, even weeks. Other government officials say they want to keep pressure on Hamas, entering deeper into urban areas to weaken it. That could embroil Israel in Gaza for weeks, possibly months.

“It is clear that, at least as far as the Israeli army is concerned, Israel’s work has not been accomplished yet,” said Giora Eiland, former head of Israel’s National Security Council, adding that the humanitarian cease-fire will “reduce pressure on Hamas.”

“Demilitarization should be the end goal, and everything short of that would be a mistake for Israel,” Eiland added.

Melman, the analyst, said he hoped there was “no hidden agenda to topple the Hamas regime,” because that could lead to more-radical militants taking control. “After Hamas, you could have ISIS,” he said, referring to the Islamic State, the group that has seized large swaths of Iraq.

It would be virtually impossible, he added, to get Hamas to give up its weapons. In killing 42 Israeli soldiers, Hamas already believes it is the victor and has the upper hand, he said.

The U.N.-brokered deal that ended the Lebanon war called for Hezbollah to be disarmed. Today, it is believed to be stronger than ever, its rockets still pointed at Israel.

Gearan reported from Paris. William Booth in Gaza City contributed to this report.