Last Tuesday, Israels military approved a plan to invade Lebanon to fight its dominant militia, Hezbollah. Hezbollahs leader issued his strongest threats against Israel in years the following day. And the U.S., Israels most powerful ally, has indicated that it will not block an Israeli offensive.

Thats just the past week. Over the nine months prior, more than 150,000 people on either side of the Israeli-Lebanese border have fled their homes as alternating rounds of Hezbollah rockets and Israeli airstrikes have steadily expanded. The attacks have extended beyond the two sides border combat facilities, killing nearly 100 Lebanese civilians and 10 Israeli civilians, rendering southern Lebanon uninhabitable and striking journalists , the U.S.-backed Lebanese military and even Lebanons capital of Beirut.

Yet the U.S. and Israel argue they can still avoid a new Middle East war in Lebanon, a conflict that would be catastrophic and worsen regional instability already exacerbated by the Gaza conflict.

In public remarks at the Pentagon on Tuesday, Defense Secretary Lloyd Austin and his Israeli counterpart Yoav Gallant projected hope for U.S.-led attempts at a deal between Israel and Hezbollah that prevents all-out fighting. Negotiations can prevent terrible consequences, Austin said, while Gallant spoke of working closely together to achieve an agreement that convinces his country and its Lebanese foe to cease hostilities.

The underlying issue is whether Hezbollah maintains its huge presence in southern Lebanon, spitting distance from northern Israel which violates a United Nations resolution and which Israel sees as an intolerable threat following the Oct. 7 attack that Hezbollahs ally Hamas, a Palestinian militant group, launched across its border with Gaza, killing nearly 1,200 Israelis, mostly civilians. After Israel initiated its retaliatory campaign into Gaza, Hezbollah began barrages into Israeli territory it cast as in solidarity with Hamas, and Palestinians broadly, as the U.S.-backed Israeli campaign has spurred mass devastation, tens of thousands of civilian deaths and mass hunger and disease. Israel, in turn, presents its strikes within Lebanon as defensive, calling harm to civilians unintentional.

The U.S. and Israeli governments claim their current approach bolsters diplomacy because it is linked to a timeline: If conditions in the Gaza Strip ease, Hezbollah may halt its assault and compromise, some U.S. and Israeli officials believe . Israel says it will conclude its large-scale offensive in Gaza within weeks, and on Tuesday, Israeli national security adviser Tzachi Hanegbi linked that possible shift to chances of a bargain for Lebanon.

But for now, the danger of an Israel-Hezbollah war is higher than it has ever been, Biden administration officials and national security experts say and many insiders are skeptical that President Joe Biden can ultimately avert it.

The core of the concern is the defining theme of Bidens Middle East policy since Oct. 7: the U.S.s overwhelming support for Israel.

As Israels chief military and diplomatic backer, the U.S. has the most influence of any outside party over its decisions, and is widely perceived as implicated in them. At the same time, its Israel that analysts and officials see as more likely to initiate a full-scale war, because Hezbollah has indicated through its statements and relatively measured attacks that it wants to keep the fighting limited.

Such a conflict could rapidly escalate, and if the two sides start pummeling each other and causing huge damage, the U.S. and Hezbollahs chief supporter, Iran, will face major pressure to get involved. Tehran and Washington already oppose each others regional presence, and in Iraq and Syria, U.S. forces and Iran-backed fighters are in close proximity, raising the human stakes of heightened tensions. A top pro-Iran militia in Iraq recently indicated that should Hezbollah face attacks, it would target U.S. interests.