JERUSALEM — Israel sought on Wednesday to fend off growing international pressure over civilian casualties from its military assault on Gaza, saying it would expedite and increase humanitarian aid and work with its allies to build a durable, long-term truce. But Israel would not agree to a proposed 48-hour cease-fire.

The government said it would push ahead with its air, sea and ultimately ground operation, which one senior military official described as “making Hamas lose their will or lose their weapons.”

A strike Thursday morning included the Parliament building among its targets, news agencies reported.

During the five days of combat, Israeli warplanes have been destroying buildings once considered off limits, including mosques and government and university compounds, with officials asserting that rocket launchers and ammunition were made, stored and even operated from there. They were also hitting the homes of militants, smuggler tunnels and even money exchange shops to choke off Hamas from its suppliers.

The military official said that Gaza was limited in size and cut off from the outside and that Israel could win if it stopped future supplies and destroyed enough of what Hamas had. He added, however, that targets were running short, and that a limited ground operation aimed at destroying remaining sites was likely once the wet weather cleared.

Meanwhile, overwhelmed hospital officials in Gaza said that of the more than 390 people killed by Israeli fighter planes since Saturday, 38 were children and 25 women. The United Nations, which has estimated the number of dead to be between 320 and 390, said 25 percent of those killed were civilians. Israel said that it was still checking the numbers.

In the Jabalya Refugee Camp north of Gaza City, hundreds lined up for hours in the rain for bread and other staples as F-16 jets menaced overhead. At one point, two rockets were launched from within the camp — among about 60 shot into Israel on Wednesday — and an Israeli missile then hit the launcher.

The rockets that have been sent some 20 miles into the Israeli cities of Ashkelon, Ashdod and Beersheba in recent days are known as grads. They measure nine feet in length with warheads that weigh 30 to 40 pounds and were not manufactured in Gaza but were bought abroad and smuggled through tunnels from Egypt, Israeli officials said.

In Shifa Hospital in Gaza City, emergency personnel engaged in a brutal form of triage, allowing the worst cases to fade as they found themselves unable to cope.

A senior Israeli official said the country was seeking ways to increase humanitarian aid so that its military endeavor could continue without further pressure to stop. It permitted a dozen wounded and ill Gazans into Israel on Wednesday for treatment at hospitals here and allowed in some 100 trucks of food and medicine.

He also said that one limitation on the aid was that crossing points had come under attack by Hamas. A second, he said, is that donors are not bringing enough goods. Of the donations so far, some come from United Nations agencies, but most are from private donors.

Tens of thousands of Gazans have received recorded phone calls from the Israeli Army warning them that their houses have been marked as targets because they harbored either militants or weapons facilities like rocket workshops. Noncombatants were urged to clear out. Hundreds of thousands of leaflets gave the same message.

Israeli officials say their goals for a truce include a complete cessation of rocket and mortar fire from Gaza, a ban on armed men approaching the border with Israel, full Israeli control over the border crossings and a mechanism to ensure that Hamas is meeting its commitments.

The Hamas leader, Ismail Haniya, told Israel that there would be no talk of a truce until it ended its attack and all the crossings into Gaza from Israel as well as from Egypt were opened to full commercial traffic. He did not mention the rockets that Israel considers the central cause of its campaign.

On Thursday, Foreign Minister Tzipi Livni was expected to fly to Paris to meet with Foreign Minister Bernard Kouchner and President Nicolas Sarkozy, who are seeking ways to promote a cease-fire.

From his ranch in Crawford, Tex., President Bush called Prime Minister Ehud Olmert. A White House spokesman, Gordon D. Johndroe, said Mr. Olmert had “assured President Bush that Israel is taking appropriate steps to avoid civilian casualties” in Gaza. In addition, he said, the Israeli leader told Mr. Bush that Israel was “targeting only Hamas operatives and those affiliated with Hamas.”

They discussed prospects for a cease-fire — “what steps could lead to a cessation of violence,” Mr. Johndroe said — but did not “get into specific timetables.”

“It all begins with Hamas agreeing to stop firing rockets” into Israel, Mr. Johndroe added. “The onus is on Hamas.”

The White House praised the diplomatic efforts of Egypt, Jordan and Saudi Arabia, but denounced Iran and Syria, saying they had supplied weapons to terrorist groups.

“Hamas is pretty well supplied by Iran and, to a certain extent, Syria,” Mr. Johndroe said. “Neither Iran nor Syria is playing a helpful role. They’re not playing a constructive role in this current crisis, which is pretty typical for their actions with regard to Hamas and Hezbollah.”

Israel’s Supreme Court told the government on Wednesday to allow foreign journalists limited access to Gaza, which had been closed to them since early November. The ruling, which urged the government to allow in a group of up to a dozen foreign journalists, came in response to a petition filed by the Foreign Press Association.

Mahmoud Abbas, the president of the Palestinian Authority, based in the West Bank, appealed to the United Nations Security Council for a cease-fire. Mr. Abbas, whose troops were forcibly ejected from Gaza by Hamas 18 months ago, is in a delicate position of not wishing Hamas to triumph but not wishing Palestinians to suffer.

In a speech delivered on Wednesday, Mr. Abbas reiterated that Hamas was responsible for the Israeli invasion because it ended the cease-fire between it and Israel 12 days ago. But he called what Israel was doing “the bloodiest massacre and systemic destruction of all forms of life; it is an aggression that does not target Gaza only but the entire Palestinian people and their cause and future and their most basic human rights.”

In the West Bank, the Palestinian police and security forces have had their leaves canceled. Some men associated with Hamas have been detained, and strict rules have been established for demonstrations in support of Gaza to avoid their turning into support for Hamas. Slogans and flags are limited, and close contact with Israeli forces and checkpoints has been barred to prevent trouble.

In Cairo, Arab countries appeared deeply divided over how to respond to the latest escalation in fighting between Israel and Hamas, with sharply differing comments from foreign ministers at the opening of an emergency Arab League meeting.

Moderate Arab states generally allied with the United States blamed Palestinian disunity for the crisis and more radical states, some of whom did not attend, urged collective action to defend the Palestinians against Israel.

In the most striking comments, Saudi Arabia’s foreign minister, Prince Saud al-Faisal, criticized the Palestinians for their inability to remain united behind President Abbas of Fatah — an implicit condemnation of Hamas, which took over Gaza entirely in 2007 in a brief but violent civil war with Fatah. Normally, during periods of Israeli-Palestinian fighting, Arab leaders condemn only Israel.

“This terrible massacre would not have happened if the Palestinian people were united behind one leadership, speaking in one voice,” Prince Saud said at the league meeting’s opening. “We are telling our Palestinian brothers that your Arab nation cannot extend a real helping hand if you don’t extend your own hands to each other with love.”