JERUSALEM — Israel stepped up its diplomatic activity on Thursday, possibly to try to gain more time for its rolling military offensive against Hamas in Gaza while keeping up airstrikes against the radical Islamic group’s infrastructure for a sixth day.

Foreign Minister Tzipi Livni left for a brief visit to France where she was to meet with President Nicolas Sarkozy and other French officials for “an exchange of opinions and ideas” and to share information about Israel’s intentions and plans, an Israeli official said. France is seeking ways to promote a cease-fire.

At the same time, Israeli air and naval forces bombed Hamas security installations, tunnels used for weapons smuggling and militants’ houses as well as symbols of government like the Parliament building and the Ministry of Justice, the Israeli military said. Israeli troops and tanks massed along the border with Gaza remained poised for a possible ground attack.

Hamas continued to fire rockets into southern Israel, hitting an eight-story apartment building in the port city of Ashdod at noon on Thursday, causing extensive damage but no serious injuries.

In Gaza, medical officials said the number of Palestinians killed in the Israeli bombardment has reached 400. While many of the dead were Hamas security personnel, the United Nations said a quarter of those killed were civilians. Israeli officials have put the number of Palestinian civilians killed at closer to 10 percent.

Israel on Wednesday rejected a proposal by Foreign Minister Bernard Kouchner of France for a 48-hour lull in fighting for humanitarian purposes. The Israeli official, who was speaking on condition of anonymity because he was not authorized to comment publicly on the proposal, called it “unrealistic,” “hasty” and bordering on “offensive,” saying that Israel was already allowing humanitarian supplies into Gaza every day.

The European Union, in a statement on Wednesday, called for an “immediate and permanent cease-fire including an “unconditional halt to rocket attacks by Hamas on Israel and an end to Israeli military action.”

But as she left for Paris on Thursday, Ms. Livni told Israel Radio that Israel would not agree to a cease-fire at this point and would continue with its military operation, the radio said. The radio cited Ms. Livni as saying “This is not a short battle and it is not a single battle, and we have long-range goals.”

Speaking to reporters on Wednesday in Sderot, an Israeli town near the border with Gaza that has been targeted by Palestinian rocket attacks for years, Ms. Livni appealed to the international community to give their support to Israel and to give Israel time, “so that at the end of this military operation, the outcome will be victory for those who believe in our values.”

Mr. Sarkozy is now scheduled to stop in Israel on Monday during a tour of the Middle East.

Israel’s stated goal for its military operation is to halt the rocket fire from Gaza and to create a new security equation in southern Israel, where three civilians and a soldier have been killed in rocket attacks in the last six days.

It has not declared its intention of toppling Hamas, which won Palestinian parliamentary elections in 2006, then took full control of Gaza after routing forces loyal to the rival Palestinian Authority in June 2007.

But in attacking important symbols of government on Thursday, Israel seemed to be blurring the lines. Israel, like the United States and the European Union, classifies Hamas as a terrorist group. The military said in a statement on Thursday that Hamas government sites “serve as a critical component of the terrorist groups’ infrastructure in Gaza.”

Ms. Livni emphasized in Sderot that Israel would not accept Hamas rule as legitimate unless the organization fulfilled conditions set by the international community including recognizing Israel, renouncing all violence and accepting previous agreements between Israel and the Palestinians, conditions that Hamas has so far rejected.

Israeli officials have said they will work with Israel’s allies to build a long-term truce, and would seek to expedite and increase humanitarian aid to Gaza alongside the military offensive, which one senior military official described as “making Hamas lose their will or lose their weapons.”

During the six days of combat, Israeli warplanes have attacked sites 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 those sites. They continued hitting smuggler tunnels and even money exchange shops to choke off Hamas from its suppliers.

The senior military official said that Gaza was limited in size and cut off from the outside and that Israel could win if it shut off 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.

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.

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.

Israel Pursues Diplomacy but Presses Attacks – NYTimes.com