Biden is walking a diplomatic tightrope regarding Israel and Iran

The coordinated action seems to have reignited some of the old warmth. The White House now hopes it can take advantage of this to influence Israel's response.

Officials are not so naive as to think there will be no reaction at all, but they want it to be calibrated such that it can be seen as an act of restraint.

But the weekend's joint military success also masks a fundamental and troubling change in the regional situation, according to former US envoy Dennis Ross, a 40-year veteran US diplomat in the Middle East.

He says Iran's direct retaliation against Israeli territory over the targeting of elite officers in its Quds Force in a raid on the Iranian consulate in Syria has “rewritten the rules” of the relationship between Israel and Iran, further destabilizing an already precarious situation.

Iran has spent years building proxy forces sworn to destroy Israel, while funding and arming Palestinian groups including Hamas, as well as the Shiite militant group Hezbollah in Lebanon.

But Saturday was the first time since the 1979 Islamic Revolution that Iran attempted a direct attack on Israel. Thus, regardless of how successful military technology has been in effectively neutralizing Iran's actions, the point of no return has been crossed.

Ross says this means there has been a “failure of deterrence” towards Iran.

He says Biden now faces an uncomfortable paradox. The president must simultaneously lower the temperature with Iran, but at the same time, he must make Tehran understand that there is a cost to its actions.

In the wake of Saturday's attack, the White House made clear that it would not join any Israeli military response against Iran, while stressing that its commitment to Israel's security remains “iron-tight.”

Iran's direct involvement in the current war would also make it more difficult to reach a ceasefire agreement in Gaza and release the hostages kidnapped by Hamas.

American diplomats are working around the clock to persuade Israel to agree to stop fighting for six weeks to allow the release of hostages from Gaza and Palestinian prisoners in Israeli prisons.

The agreement would also facilitate the movement of much-needed aid to Gaza, where famine looms. Before the weekend, they had the support of Israel and the pressure was on Hamas.

All of this is now in jeopardy as the world waits to see how Israel will respond.

Meanwhile, the president's domestic complexities remain ever-present. There is pressure from parts of the left to distance itself from Israel. Accusations from the right of weakness for not standing up to Iran with sufficient force.

“I get it in an election year,” says Ross, who played a key role in the Middle East peace process in the George H.W. and Clinton administrations. “You want to keep things under control. That's completely understandable.”

He added: “But by the same token, we have Iran taking a step that it had never taken before. By taking this step, it is showing a willingness to cross certain thresholds, and the more they cross certain thresholds, the more accustomed they become to it.” “As a result, the area becomes much more dangerous.”

All of this, of course, carries the potential for misunderstanding and miscalculation.

One mistake can set off a chain reaction that can quickly spiral out of control.

The area is a notorious gunpowder zone and the lights could flare up more at any time.

The world is holding its breath.