Hours before Secretary of State Condoleezza Rice arrived here for talks on resolving the Middle East conflict, Israel increased the pressure Wednesday on Hamas, the militant Islamic group in control of the Gaza Strip, by declaring Gaza “hostile territory.” The move opened the way for further restrictions on the supply of crucial goods like electricity and gasoline to Gaza.

Israeli officials said the purpose of the declaration, by Israel’s security cabinet, was to hold Hamas accountable for any further rocketing or other attacks on Israel from Gaza, which Hamas took over when it routed Fatah forces in June.

Asked about the Israeli decision, Ms. Rice said, “Hamas is a hostile entity to us as well.” Both Israel and the United States, as well as the European Union, classify Hamas as a terrorist organization, and Hamas has refused international demands that it recognize Israel’s right to exist, forswear violence and accept all previous Israeli-Palestinian agreements.

“We won’t allow Hamas to hide behind other groups like Islamic Jihad,” one Israeli official said, referring to the fact that many rockets are being launched by another militant group. “Hamas is doing everything now except firing the rockets, and we intend to hold them responsible.”

The cabinet statement said “additional sanctions will be placed on the Hamas regime in order to restrict the passage of various goods to the Gaza Strip and reduce the supply of fuel and electricity,” as well as to tighten restrictions on the movement of people in and out of Gaza.

Israel is not taking action yet, the officials emphasized, but one said that “a clock is ticking” on carrying out the measures.

The Israeli defense minister, Ehud Barak, told the cabinet, “The objective is to weaken Hamas,” and he said that “every day that passes brings us closer to an operation in Gaza.”

A senior Israeli official said, “We will supply all humanitarian necessities,” including food, water and medical supplies.

“But that doesn’t mean they can drive their cars all around Gaza,” the official said. “That’s not a humanitarian need.” The official said Israel now supplied 60 percent of Gaza’s electricity. “No one will cut off the electricity, but in response to direct attacks, we could hold Hamas responsible, and there may be some interruptions in electrical supplies.”

Hamas reacted sharply. Sami Abu Zuhri, a Hamas spokesman in Gaza, called the Israeli decision “a declaration of war against the Palestinian people, an attempt to target resistance forces and to undermine Hamas politically.” He said that Israel as an occupier must supply humanitarian needs, and that such a decision “shows that Israel is not ready for political compromise with the Palestinians” in peace talks.

On Tuesday, the Hamas leader in Gaza, Ismail Haniya, met with Islamic Jihad to ask it to stop firing rockets for now, during the current holy month of Ramadan, and Hamas leaders in exile in Damascus will meet with Islamic Jihad leaders there to discuss a renewed cease-fire with Israel.

In New York, the United Nations secretary general, Ban Ki-moon, warned that any cutoff of electricity or water to Gaza would violate international law and punish Palestinian civilians.

“Such a step would be contrary to Israel’s obligations toward the civilian population under international humanitarian and human rights law,” Mr. Ban said in a statement. “I call for Israel to reconsider this decision.”

A senior United States official, speaking on the condition of anonymity because he was not authorized to comment on the matter publicly, said American officials had urged the Israelis to consider the humanitarian consequences in Gaza. He said Ms. Rice was not informed of the decision before she arrived.

Under international law, Israel is considered an occupying power in Gaza, even though it has removed its troops and settlers from the territory. Denying civilians access to the necessities of life is considered collective punishment and a violation of international law under both the Hague and Geneva Conventions, although the amounts of resources like electricity considered essential could be subject to dispute.

Electricity, water and gasoline are considered by many, like the Israeli rights lobbying organizations B’Tselem and Gisha, as well as Oxfam and other aid and rights groups, to be necessities. But the United States contended when it bombed power plants in Belgrade during the Kosovo war that electricity furthered Serbia’s war effort. Israel made a similar case when it bombed Gaza’s main power station in July 2006, after the capture of one of its soldiers.

“Regardless of how they might cloak it, cutting off electricity to a civilian population is collective punishment and a violation of international law,” said Sarit Michaeli of B’Tselem. “It doesn’t really make a difference whether it’s cutting off the supply from Israel or bombing the power station.”

Israel says it will not cut off water, but most of Gaza’s water is indigenous, pumped from wells with electricity. Electricity is also important for sewage treatment, Ms. Michaeli said. She condemned the Qassam rockets fired from Gaza and said that Israel was legally obligated to defend Israelis, but not by violating international law.

Ms. Rice is here to press both the Israeli prime minister, Ehud Olmert, and the Palestinian president, Mahmoud Abbas of Fatah, to come up with a joint set of peace principles before an international meeting for which she will be the host, expected to be in Washington in mid-November.

Hamas opposes Mr. Abbas’s talks with Mr. Olmert, but expects them to go nowhere.

Ms. Rice also said that the United States would not “abandon the innocent Palestinians” in Gaza. Privately, Bush administration officials said that they had been assured that Israel would not deny essential humanitarian supplies to Gazan civilians.

Ms. Rice intends the November conference to tackle what she called the “critical issues” of Palestinian statehood. But plans for the conference remain vague, and both Mr. Olmert and Mr. Abbas are worried about raising expectations.

Saudi Arabia has said it will not attend unless the conference addresses the final status issues that have bedeviled peace negotiators since 1979: the status of Jerusalem, the fate of Palestinian refugees who left, or were forced to leave, their homes, and the borders of a Palestinian state.

Mr. Abbas’s aides have said that he will ask Ms. Rice on Thursday not to set a firm date for the meeting until it is clear that he and Mr. Olmert can agree on a detailed joint statement. Israeli officials say the two men are talking substantively and interpreted Palestinian worries now as a form of lobbying of Ms. Rice.

“I’ve been very clear that this meeting has to, in a substantive way, support the activities and the efforts of the parties to lay a foundation for the negotiation of a Palestinian state as soon as possible,” Ms. Rice told reporters en route to Jerusalem. “I think everybody expects it to address critical issues and, you know, we don’t expect anything less.”

But it was clear during her news conference with Tzipi Livni, Israel’s foreign minister, that Israel had not yet signed on to a discussion of final status issues. “I believe in realistic expectation,” Ms. Livni said when asked if Israel was prepared to discuss final status. “Of course we would like to end the conflict right away.” But, she added, “we need to find what are the common denominators.”

Ms. Rice met with other senior Israeli politicians later on Wednesday and had a private dinner with Mr. Olmert that night, before meeting with Mr. Abbas and Palestinian officials in Ramallah on Thursday.