Rockets are flying from Gaza into southern Israeli communities again. Israeli warplanes are firing missiles back, and Israel is closing the crossings through which food and fuel are supplied. The United Nations agency that feeds Palestinian refugees in Gaza says its stocks of flour are exhausted.

In other words, the six-month truce that Israel and Hamas, the militant Palestinian leaders of Gaza, agreed to on June 19 is over. On Friday, Hamas officially declared in a statement that the ceasefire had expired, saying the truce would not be renewed because Israel was failing to fulfill its “fundamental conditions and obligations.” The end of the truce was greeted by relative calm, with only a scattering of rocket attacks and no major Israeli military activity. Officials and analysts on both sides say that things are likely to deteriorate further in the short term, but that both sides need the truce, so they will probably grope their way back to it. The question is how soon and after how much suffering.

Israel and Hamas accuse each other of bad faith and of violations of the Egyptian-mediated accord, and each side has a point. Rockets from Gaza never stopped entirely during the truce, and Israel never allowed a major renewed flow of goods into Gaza, crippling its economy. This is at least partly because the agreement had no mutually agreed text or enforcement mechanism; neither side wanted to grant the legitimacy to the other that such a document would imply.

“I think it is going to get a lot worse before it gets better,” remarked Robert A. Pastor, who has been traveling in the region with former President Jimmy Carter, meeting with Hamas and other officials. “It did lead to a significant reduction in the number of rockets fired at Israel until November, but the truce had less impact on the goods going in. One hopes both sides learn lessons and agree on a text and publicize it.”

There seems little likelihood of that happening soon. Hamas considers Israel an illegitimate state and is doctrinally committed to its destruction, while Israel views Hamas as a terrorist group that must be dismantled. Yet each needs the other to hold its fire. That is why negotiations over another truce have started, again through Egypt. Separately, the Palestinian president, Mahmoud Abbas, was due to hold what is likely to be a final meeting with President Bush in Washington on Friday to discuss peace negotiations. He had called for Hamas to renew the truce.

Hamas officials say it was their understanding at the time that two weeks after the June 19 accord took effect Israel would open the crossings and allow the transfer of goods that had been banned or restricted after June 2007, when Hamas waged a violent takeover of Gaza.

Their job, the Hamas officials said, was to stop the rocket attacks on Israel not only from its own armed groups, but also from others based in Gaza, including Islamic Jihad and Al Aksa Martyrs Brigades.

It took some days, but they were largely successful. Hamas imposed its will and even imprisoned some of those who were firing rockets. Israeli and United Nations figures show that while more than 300 rockets were fired into Israel in May, 10 to 20 were fired in July, depending on who was counting and whether mortar rounds were included. In August, 10 to 30 were fired, and in September, 5 to 10.

But the goods shipments, while up some 25 to 30 percent and including a mix of more items, never began to approach what Hamas thought it was going to get: a return to the 500 to 600 truckloads delivered daily before the closing, including appliances, construction materials and other goods essential for life beyond mere survival. Instead, the number of trucks increased to around 90 from around 70.

Israeli officials acknowledged that transferring previously banned goods had been the plan, but said that there was no specific date for the increase and that it was to happen in steps. But the rockets never fully stopped.

“The Palestinians wanted to have one or two rockets a week to keep our people in tension and still tell people inside Gaza, ‘See, we continue to fight and we continue to bring in goods,’” said Shlomo Dror, chief spokesman for Israel’s Defense Ministry. “The moment we fail to react to one rocket we encourage them. Our only choice was to close the crossings when rockets came in.”

In addition, Israeli forces continued to attack Hamas and other militants in the West Bank, prompting Palestinian militants in Gaza to fire rockets. The Israeli military also found several dozen improvised explosive devices used against its vehicles on the Gaza border and about a dozen cases of sniper fire from Gaza directed at its forces.

While this back-and-forth did not topple the agreement, Israel’s decision in early November to destroy a tunnel Hamas had been digging near the border drove the cycle of violence to a much higher level. Israel says the tunnel could have been dug only for the purpose of trying to seize a soldier, like Cpl. Gilad Shalit, the Israeli held by Hamas for the past two and a half years. Israel’s attack on the tunnel killed six Hamas militants, and each side has stepped up attacks since.

Israel was actually hoping that the agreement would lead to progress on Corporal Shalit’s release, or at least to increased information on his condition or negotiations over an exchange for him. But Hamas said the Shalit case was entirely separate from the accord, just as Israel had rejected the request by Hamas to have the truce suspend attacks on its men in the West Bank. There, too, Hamas had hopes that the accord would create some changes that did not take place.

Israel’s focus on Corporal Shalit and Hamas’s focus on the West Bank are examples of why the agreement, without a text or enforcement mechanism, has been so problematic, with each side relying on its own desires rather than on mutually agreed steps. But given each side’s refusal to acknowledge the other’s legitimacy, another such accord of winks and nods seems the likely outcome of any coming negotiations.