The war in the Middle East is escalating fast – and Biden has squandered too many chances to stop it | Mohamad Bazzi

I recently returned from three weeks in Lebanon, where I found people braced for an incident that might escalate into a full-scale war between Israel and Hezbollah. The past week’s retaliations in the region look worryingly like exactly these kinds of clashes. Each strike and counterattack between Israel and its enemies increases the risk that its catastrophic war on Gaza could spiral into a regional conflict with Iran and its allied militias in Iraq, Lebanon, Syria and Yemen. Joe Biden has said that his main priority is preventing such a war. The next few days, then, could prove critical.

On Tuesday evening, an Israeli airstrike on southern Beirut killed a senior Hezbollah commander, Fuad Shukr, whom Israel blamed for orchestrating a rocket attack days earlier which had killed 12 children. Shukr’s killing was overshadowed hours later by the assassination of Hamas’s political leader, Ismail Haniyeh, in Tehran early on Wednesday. That attack shocked and embarrassed Iran’s leaders, who were hosting Haniyeh and dozens of other allies for the inauguration of the new Iranian president.

The brazen assassination of Haniyeh was particularly humiliating for Iran’s Revolutionary Guards, who are charged with protecting visiting foreign dignitaries and coordinating the so-called “axis of resistance”, a number of regional militias funded and supported by Iran, which includes Hezbollah and Hamas. Iran has vowed to avenge Haniyeh’s killing on its soil.

But Shukr’s assassination has the potential to be an even deadlier powder keg because it straddles a faultline that has come closest to igniting a regional war beyond Gaza: the Israel-Lebanon border. In a speech via video link at Shukr’s funeral on Thursday , the leader of Hezbollah, Hassan Nasrallah, made clear that his group will retaliate for the commander’s killing and warned that the conflict with Israel had entered a “new phase”.

Nasrallah said Israel had crossed a “red line” by attacking Haret Hreik, a densely populated Shia neighbourhood in the southern suburbs of Beirut, where a number of Hezbollah leaders live and the group has multiple offices. In the past, Nasrallah has threatened to retaliate for any Israeli attack on Beirut or its suburbs by launching missiles and rockets at Tel Aviv. Shukr was a longtime Hezbollah official who was reportedly close to Imad Mughniyeh, the group’s former military commander and mastermind of the 1983 bombing of the US marine barracks in Beirut. The US had offered a $5m bounty on Shukr for his alleged role in the bombing, which killed 241 US military personnel.

While Shukr had been in Israel’s sights for years, his assassination came after the Israeli military said he was responsible for a rocket attack on 27 July on a football pitch in a remote town in the Israeli-occupied Golan Heights, which killed 12 children. Israel and the US accused Hezbollah of the deadly strike on the town of Majdal Shams, and the Israeli prime minister, Benjamin Netanyahu, promised a “severe” response .

Hezbollah denied responsibility for the attack, though it admitted firing a barrage of rockets earlier in the day at nearby Israeli military installations in the Golan Heights. Hezbollah and its supporters claim that the explosion on the football field was caused by a malfunction in Israel’s Iron Dome missile defence system, which is used to shoot down incoming rockets. Despite the competing accounts, this is exactly the kind of incident that many people in the Middle East have feared would lead to an escalation that would unleash a full-scale war between Israel and Hezbollah, the most powerful member of Iran’s “axis of resistance”.

A day after the 7 October attack by Hamas militants on southern Israel, Hezbollah began firing rockets and drones into northern Israel – in what the Lebanese militia’s leaders described as an act of solidarity with Palestinians that was meant to divert Israeli military resources away from Gaza. Israel has retaliated with heavy airstrikes and artillery shelling across southern Lebanon, which has killed about 350 Hezbollah fighters and more than 100 civilians, including children and medics. The Israeli military said, as of Tuesday, at least 25 civilians and 18 soldiers have been killed by Hezbollah attacks since October. Tens of thousands of civilians on both sides of the border have been forced out of their homes.

The near daily exchange of fire across the Israel-Lebanon border has ebbed and flowed, as Israel’s brutal war on Gaza intensified over the past nine months. All along, despite bluster from hardline Israeli politicians and military officials, Israel and Hezbollah have insisted that they don’t want a wider war, which would be devastating to both countries. But as each side tests the other’s limits, there is a greater danger that the conflict could spread beyond the border areas, by accident or miscalculation – if not by design.

Before Tuesday’s airstrike on Beirut, Israeli officials told western media that their response would lead to a few days of intensified fighting. But neither side has a clear path to de-escalate even within a couple of days. It seems that Netanyahu ignored the US administration’s pleas to avoid targeting Beirut or its southern suburbs, so that Hezbollah would be less likely to escalate in response.

A full-scale war between Israel and Hezbollah, similar to the one the two sides fought in the summer of 2006, could entangle Israel and the US in a wider conflict with Iran and its allies. For its part, Iran has used militias – including Hamas, Hezbollah, the Houthis in Yemen, and several Shia groups in Iraq and Syria – to strike at Israeli and US targets across the region in an attempt to increase pressure on them to stop the Gaza war.

Related: Israel has all but declared war in the Middle East – a conflict it cannot hope to win | Simon Tisdall

Since October, Biden and his top aides have insisted that their highest priority is to prevent Israel’s invasion of Gaza from spreading into precisely this kind of regional conflagration. But Biden has avoided the most straightforward path to de-escalation on all fronts: for the US administration to withhold some of the $6.5bn in weapons and other security assistance it has promised to Netanyahu’s government since October, and pressure Netanyahu to accept a ceasefire. Instead, Biden has squandered the significant leverage he has over the Israeli premier, who some accuse of trying to prolong the Gaza war to dodge a series of corruption charges that have dragged through the Israeli courts for years, and an independent inquiry into his government’s security failures leading up to 7 October.

One of the Biden administration’s biggest mistakes over the past few months has been to frame the protracted ceasefire negotiations between Hamas and Israel as only focused on Gaza, without recognising that all of Iran’s allies in the region, especially Hezbollah and the Houthis, have made clear that they too would stand down once the fighting stops in Gaza.

There has been one sliver of hope in recent weeks: the Biden administration has been signalling to Netanyahu’s government that it may not receive the kind of extensive US military support it would need to launch a full-scale war in Lebanon. But to prevent the conflict between Israel and Hezbollah from spinning out of control, the US and its western allies must insist on an immediate ceasefire in Gaza – and that Netanyahu stop escalating regional attacks and goading Iran and its allies into a devastating war. The alternative is a descent into further bloodshed and wanton destruction.

• Mohamad Bazzi is director of the Hagop Kevorkian Center for Near Eastern Studies, and a journalism professor at New York University