The Arak IR-40 heavy water reactor in Iran. Photo: Nanking2012/Wikimedia Commons.

It is becoming increasingly difficult to mask the gap between Washington and Jerusalem on how best to deal with Iran’s nuclear program.

In particular, attention is focused on the P5+1 talks with Iran, the next round of which will take place in Geneva this week, on November 7-8.

The Obama administration wants Congress to hold off on additional sanctions, at least for a few months. This reflects a desire to demonstrate America’s sincerity in the talks, while testing Iranian intentions. If the talks fail, the U.S. says it will support new legislation.

But it’s clear that, for Israel, such an approach sends the wrong signal to Tehran.

Whatever the rhetoric from the Iranian president and foreign minister, actions speak louder than words. Those actions, Jerusalem insists, show no change on the litmus-test issues – from spinning centrifuges, to plutonium reprocessing, to ballistic missile development; from complicity in war crimes in Syria to massive human rights violations at home; and no shift in the outlook of the top Iranian decision-maker, Supreme Leader Ayatollah Ali Khamenei. Indeed, on November 3rd, he declared Israel to be an “illegitimate, bastard regime.”

Moreover, reading between the lines, there are those Israeli officials – not to mention Saudi, Kuwaiti, and other Gulf leaders – who wonder if the U.S. is risk-averse to any possibility of military conflict, after the costly forays into Afghanistan and Iraq, not to mention the erratic course on Syria, even if it means a less-than-ideal agreement with Iran.

And still more problematic, they fear, that may be Iran’s conclusion as well, emboldening Tehran to believe that it may have the upper hand in the talks. After all, at the end of the day, in addition to the sanctions, it is the credibility of the U.S. military threat that is most likely to be determinative in Iranian thinking on how best to proceed.

Thus, Israel finds itself in an excruciatingly difficult position.

Prime Minister Benjamin Netanyahu faces what could be the most challenging decision of any Israeli leader since 1973, if not 1948. He is grappling not only with how best to defend Israel’s national security against an ominous threat, but also, at the same time, how to manage his relationship with Israel’s indispensable ally, the U.S.

If he concludes he cannot trust the P5+1 talks, and that a point will come beyond which Israel may no longer have viable military options, he will have to weigh carefully the benefits and costs of going it alone.

To do so risks a clash with Washington, if, for instance, the Obama administration is convinced the negotiations remain worth pursuing. And that could have major consequences, not only bilaterally but also multilaterally.

After all, the P5+1 consists of the five permanent members of the UN Security Council (plus Germany), the only countries with the veto in a UN body that has legally enforceable powers.

Meanwhile, for the U.S. Senate, two options have emerged.

The first, proposed by the administration and cited earlier, is to seek a delay of at least a few months in the consideration of a new sanctions measure. The logic is that a pause will show American good faith to Iran and also assure our partners in the P5+1.

The second, supported by some leading Democrats and Republicans, is to press ahead. The thinking here is that sanctions brought Iran to the table in the first place, and more sanctions will keep it at the table and likelier to compromise on the big issues.

The latter option is the more compelling of the two.

It would send a clear signal that, while the U.S. is prepared to negotiate earnestly, as long as there is no clear evidence of Iran’s change of behavior, the sanctions will continue to be tightened.

Since it is the ever-toughening sanctions that got Iran to negotiate in the first place, there needs to be a reminder that things will get still worse for Tehran if nothing changes soon on the ground. Elaborate efforts on Iran’s part to buy time – with Tehran’s mastery of modulated feints, nods, winks, and hints of openness – just won’t wash.

Even so, the new Senate measure – which is still in committee and needs to be adopted, and then reconciled with House language (adopted earlier this year) before it can be enacted into law – wouldn’t go into effect immediately, so the administration would be able to point to what lies ahead if the Iranians don’t cooperate now.

And finally, it would offer additional assurances to key U.S. allies – not just Israel, but those Arab countries fearful of Iran’s aims and uncertain of America’s posture – that we intend to hang tough, and ensure, one way or another, that Tehran does not cross the nuclear goal line.

David Harris is the Executive Director of AJC (www.ajc.org).

This article was originally published by Ha’aretz.