President Barack Obama has offered to broker a cease-fire between Israel and Hamas, a standard U.S. response to the periodic outbreak of violence from Gaza. But the current rocket fire from Gaza into Israel is different from past episodes, and the usual cease-fire may not answer Israel's new peril.

On Wednesday, Hamas took credit for trying to destroy Israel's nuclear reactor at Dimona. Three rockets were fired at the installation. Two fell short and one was intercepted by Israel's Iron Dome anti-missile system.

Had the attacks succeeded - and more are expected - widespread exposure to nuclear radiation could have resulted. At the least, Hamas' terror campaign would have achieved a new level.

Around the same time, Hamas spokesman Sami Abu Zuhri declared, "All Israelis have become legitimate targets." He claimed that the deaths of seven civilians in an Israeli air raid on Khan Yunis, a Gaza settlement, justified this blood claim.

Israel's reply to Hamas rocket attacks has indeed been far more deadly than the provocation. But that is due to three things: the ineptness of most Hamas attacks, the roughly 90 percent success of Israel's Iron Dome system in destroying the missiles most likely to do damage, and the practice of Hamas to put its missiles, command posts and other military targets in the midst of dense civilian populations.

The New York Times reports that before Israel struck the target in Khan Yunis, where seven Palestinians died, the Israeli military called five minutes ahead and then set off a flare to warn everyone to leave the building.

Instead, reported witnesses at the scene, people rushed onto the building's roof in hopes of deterring the strike.

Israel has put up with desultory missile strikes from Gaza for years, occasionally striking back when attacks became more intense.

The last such occasion was in March 2012.

The current surge in Hamas attacks began Tuesday in apparent response to the murder of a Palestinian teen-ager in Jerusalem, itself the unjustifiable response to the murder of three Israeli teen-agers by Hamas operatives last month.

The whole attack-response cycle has had a predictable arc. Hamas shoots wildly at Israel, putting its subjects at risk of Israel's responding air raids, to show it is standing up for Palestinian rights. After harsh words, however, it declares a cease-fire, which it immediately violates, but at a less threatening level.

But this time might be different because Iran has managed to smuggle more powerful missiles into Gaza with sufficient range to cover most of Israel. One fell on a resort town east of Tel Aviv. Israel has closed the Tel Aviv airport, and is taking extra precautions at its main international airport, Ben Gurion. Both airports are within range of Hamas rockets.

The heightened threat level may lead to an Israeli invasion of Gaza.

Meanwhile, Israel also has to worry about the threat from Hezbollah in Lebanon, with as many as 30,000 missiles, including some that have GPS guidance systems. Hezbollah also gets its weapons from Iran, with the help of the Assad government of Syria. It can be expected to unleash an attack if Iran thinks it is desirable. With Iran's help Assad seems to be winning the civil war in Syria, but it is not over yet. Indeed, it has spread to Iraq and now threatens Jordan.

Hamas' aggression against Israel - the murders, the missiles, the rhetoric - threatens to drag Israel into the wider Middle East conflict. A cease-fire may put a temporary stop to the pressure from Iran's proxies.

But Israel's heightened peril will remain.

And that intensifies the need for the international community, including the United States, to help resolve not only the latest violence, but finally the intransigent Israeli-Palestinian conflict.