An Israel-Hamas truce has boiled down to a simple tradeoff: For a day of calm, Israel adds five truckloads of cows and 200 tons of cement to its shipment of the barest basics to Gaza, but also punishes sporadic rocket fire by resealing the territory for a day.

Since the cease-fire deal was reached nearly three weeks ago, the trickle of extra goods has barely made a difference in the daily lives of 1.4 million Gazans, who've been cut off from the world since the violent Hamas takeover a year ago. Gazans are struggling with fuel rationing of five gallons (20 liters) per driver a week, frequent blackouts and soaring food prices.

At the same time, the truce remains shaky and the two sides seem unable to move forward. Still, weary residents cling to hopes that this truce will stick where many others failed.

"We need to breathe," said Gaza trucker Shawki Abu Shanab, 40, who stretches scarce diesel for his flatbed truck with motor and cooking oil and has no spare parts to fix worn tires and broken lights.

Under the Egyptian-brokered deal, Gaza's Hamas rulers are to halt rocket and mortar fire on Israeli border communities, and Israel is to increase the flow of goods into Gaza. After the Hamas takeover, Israel had largely sealed the territory, allowing only basic foods and medicines to enter. Once the truce takes hold firmly, an Israeli soldier captured by Gaza militants two years ago is to be freed in a prisoner swamp.

On Tuesday, each side blamed the other for lack of progress.

Hamas has not reined in all militants, particularly those from rival groups, and the Israeli army says 15 rockets and mortars have been fired since the truce took effect June 19, including a mortar shell Tuesday. Lt. Peter Lerner, an Israeli military spokesman, said Hamas' failure is slowing a broader opening of the crossings.

Hamas says Israel closed border crossings for seven of 17 days of post-truce operations. "The calm is not shaky. The Israeli commitment to the calm is shaky," said Said Siyam, a senior Hamas official, before heading to Cairo for more truce talks with Egyptian officials.

And despite some attempts to defuse tensions, both sides have stuck to pre-truce behavior.

In Gaza, an explosion went off Tuesday in a Hamas military training camp, an apparent "work accident" that killed two militants and appeared to confirm Israeli fears that the group is using a lull to rearm. In the West Bank city of Nablus, Israel ordered an entire shopping mall shut down by August as an alleged Hamas front.

In Gaza, events of recent days illustrated how easily the truce can be derailed.

On Monday, cargo shipments appeared to be moving according to plan at the makeshift Sufa crossing between Israel and Gaza. In the morning, Israeli trucks delivered the usual staples — fruit, dairy, frozen meats — as well as a post-truce delivery of 200 tons of cement and about 100 beef cows.

Palestinian forklift operators, wearing bright yellow vests and with special security clearance, unloaded the cargo, drove it into a no-man's land and dropped it off there. After the Israelis withdrew, dozens of Gaza trucks approached and picked up the cargo. Because of the intense heat, cows were handled first, then frozen foods, dairies and other perishables.

The Gaza truckers had been waiting for hours at Sufa before they got the signal to go ahead. During their down time, they dozed on blankets spread on the asphalt and shaded by their trucks, played cards or smoked. By mid-afternoon, news spread that militants had fired a mortar shell toward the border.

The truckers were able to pick up their cargo that afternoon, but by Tuesday morning, Sufa was closed — the expected response to the mortar shell. Egyptian intelligence chief Omar Suleiman, the architect of the truce, called Israeli Defense Minister Ehud Barak and asked him to reopen Sufa.

Barak relented, and the crossing reopened Tuesday afternoon. However, another mortar shell was fired later in the day, and it remained unclear whether Sufa will open Wednesday.

Gaza militants, who usually rush to claim responsibility for rocket and mortar fire, did not do so in most of the post-truce attacks. Hamas police thwarted several border attacks, but it's not clear whether the Islamic militants, who are in tight control of Gaza, are unable or unwilling to rein in renegades.

In the meantime, Gaza's business people describe the new shipments as tiny drops in an ocean of need. Faysal Shawa, head of the Gaza Businessmen's Association, said some 4,000 businesses and workshops have been forced to shut down because of Israel's ban on Gaza trade, wiping out some 100,000 jobs.

Construction sites remain idle, and the renewed cement shipments are at best enough for small jobs.

Osama Khayel, head of the Contractors Association, said Gaza needs 4,000 tons of cement a day, or 20 times the current quantity coming in, and that building projects worth $245 million have been on hold for the past year. Key construction materials, such as steel rods, are still lacking, he said.

Lerner, the Israeli official, said that "we are not talking about returning the construction sector to full capacity." Renewed deliveries of building materials are to be used for humanitarian needs, he said. Steel rods were to be delivered Tuesday, before Sufa was briefly closed due to mortar fire, he said.

Abu Shanab, the Gaza trucker who earns just $30 dollars for a day's work at Sufa, said the militants need to start thinking about ordinary Gazans.

"We ask them to take into consideration that we live in a very bad situation," said the father of eight. "If they fire one rocket, it means we go backwards."