JERUSALEM — A civilian tragedy in Lebanon caused by an Israeli airstrike has cast doubt on any chance of bringing a quick end to almost three weeks of fighting between Israel and Hezbollah.

An Israeli airstrike against suspected rocket crews Sunday in southern Lebanon killed dozens of civilians in their sleep, shocking the international community just as the U.S. secretary of state, Condoleezza Rice, was trying to secure terms for a cease-fire.

Israel insisted the carnage in the village of Kana was an accident that occurred in the course of its self-defense.

“Nothing is more alien to our spirit, further from our thoughts, or more contrary to our interests, than hurting innocents,” Prime Minister Ehud Olmert told his Cabinet.

But he added that Israel’s offensive in Lebanon, launched after Hezbollah killed eight soldiers and abducted another two in a July 12 border raid, would continue.

“We will not flinch before Hezbollah and we will not stop the offensive, despite the difficult circumstances. It is the right thing to do,” he said.

Israel agreed Sunday to suspend its airstrikes in southern Lebanon for 48 hours, although it carried out limited strikes on Monday. U.S. State Department spokesman Adam Ereli made the announcement Sunday night in Jerusalem after Olmert met with Rice.

Israel will also coordinate with the United Nations to allow a 24-hour period for residents of southern Lebanon to leave the area, Ereli said.

Earlier Sunday, Lebanese Prime Minister Fouad Siniora called off Rice’s planned shuttle visit to Beirut just days after cautiously endorsing an Anglo-American proposal for removing Hezbollah from the violent Israeli border.

“There is no place on this sad morning for any discussion other than an immediate and unconditional cease-fire as well as an international investigation into the Israeli massacres in Lebanon now,” Siniora said.

The criticism was echoed by France and Egypt, countries that had been mentioned as possible candidates for supplying troops for an international peacekeeping force in Lebanon.

“France condemns this unjustifiable action, which shows more than ever the need to move toward an immediate cease-fire, without which other such dramas can only be repeated,” the office of French President Jacques Chirac said in a statement.

Sunday night, the U.N. Security Council issued a statement expressing “extreme shock and distress” at Israel’s killing of Lebanese civilians in a weekend airstrike. But the United States blocked a call for an immediate cease-fire in the statement issued. In its statement, the council deplored the loss of innocent lives, called for an end to violence and noted the need for “securing a lasting, permanent and sustainable cease-fire.”

Earlier Sunday, Kofi Annan urged the council to condemn the strike.

The U.N. secretary-general said the attack demonstrates the need for an immediate cease-fire.

“Action is needed now before many more children, women and men become casualties of a conflict over which they have no control,” Annan said.

Responding to Annan, Israel’s ambassador to the United Nations, Dan Gillerman, apologized for the incident, but called the Lebanese casualties the “victims of the Hezbollah.”

Gillerman said Hezbollah must be disarmed before any cease-fire occurs. Otherwise, he said, Hezbollah will rise again — “not just against us and not just against the people of Lebanon, but against the whole region and civilization as we know it.”

The deaths in Kana — which reached at least 54 — were doubly damning for the Jewish state, as the village was the site of an errant Israeli artillery shelling against Hezbollah in 1996 that killed almost 100 civilians.

Olmert said the area this year has served as a center for the firing of Katyusha rockets on the Israeli cities of Kiryat Shmona and Afula.

Warren Christopher, who as U.S. secretary of state at the time helped broker a cease-fire, chided Rice for advancing the Bush administration’s doctrine that reining in Hezbollah was key to producing a long-term solution to the Israeli-Lebanese crisis.

“My own experience in the region underlies my belief that in the short term we should focus our efforts on stopping the killing,” Christopher wrote in The Washington Post.

Israel’s failure to defeat Hezbollah or seriously stem its cross-border salvoes — another 115 landed Sunday — have raised questions about the effectiveness of military force alone.

But offsetting the doubts is anger over the mounting Israeli losses — 51 soldiers and civilians — and the

belief that Hezbollah is the vanguard of an Iranian regime that is openly preparing for all-out war with Israel.

“In Iran, they say, ‘We are targeting Israel,’ but Israel is the first western outpost. Their target is the West, period. Their rockets that they’re developing in Iran are targeted to you, they already reach us but they are arranging now rockets that will reach London,” opposition leader Benjamin Netanyahu, who in a wartime irony has become Olmert’s most eloquent foreign spokesman, said in an interview with Britain’s Sky Television.

“Beware, you’ve been warned. Don’t attack the victim, attack the attacker,” he said.