As Israel joins Saudi Arabia and other Sunni sheikdoms in their sectarian war against the Shiites, Israel’s new front may well be in Lebanon, with Israel attacking Hezbollah in a move that could also kill the Iran nuclear deal, as Trita Parsi and Paul Pillar explain.

By Trita Parsi and Paul Pillar

There are signs Israel may be at war again this summer. This time, not with Hamas in Gaza but with Hezbollah in Lebanon. Such a war may be the result not only of spillover from the Syrian war or ongoing Israeli-Hezbollah tensions. The deciding factor may be an Israeli calculation that war will shift momentum in the U.S. Congress decisively against the pending nuclear deal with Iran — a deal that critics say will increase Iran’s maneuverability in the region, including its support for Hezbollah.

In spite of AIPAC, Israeli Prime Minister Benjamin Netanyahu, the Saudis and some of its GCC allies having done everything they could to kill the pending nuclear deal with Iran, they have failed. The negotiations are on track. Many opinion polls show that a comfortable majority of Americans support President Barack Obama’s diplomacy with Iran.

If a Congressional vote on a resolution rejecting the nuclear deal were held today, President Obama probably would prevail — possibly without even having to use his veto to defeat the attempt by Republicans and pro-Netanyahu Democrats to scuttle the historic diplomatic agreement with Tehran.

Opposition arguments — from claiming that the deal is a capitulation to Iran to the notion that it is unacceptable to make a deal with a regime like that in Tehran — have not sufficiently resonated with the public to kill the agreement. This has caused some disarray in the opposition camp.

Indeed, if you are in that camp right now, it is reasonable to expect that the search is not for a new argument but for a game-changing development: an event so powerful it shifts the momentum in Congress back to AIPAC, Netanyahu, Saudi Arabia and the other opponents of a nuclear deal.

Arguably, a military confrontation between Israel and Hezbollah this summer could fit that bill. The argument that the deal — and the more than $50 billion that would be returned to Tehran — would strengthen Iran in the region and empower its allies would become much more potent if Israel were in an active conflict with Lebanon with Hezbollah rockets hitting Israeli cities, as was the case in 2006. Such a scenario can become the much desired game-changer that may cause many pro-Netanyahu Democrats to break with Obama.

All of this could be dismissed as speculative except for the fact that a case for a war with Hezbollah has been made in Israel for the past few months. On May 12, the New York Times reported that Israeli is preparing for “what it sees as an almost inevitable next battle with Hezbollah.” An Israeli official added in comments to the Times: “We will hit Hezbollah hard.”

The Israelis argue that Hezbollah is engaged in a massive military buildup, and that Israel is publicizing Hezbollah’s armament “to put the problem on the international agenda in case there is another conflict.” According to the Israeli military, Hezbollah now has the capacity to hurl 1,200 rockets a day at Israel.

Israel has been pushing this angle for several months. In February, 28 U.S. lawmakers came to Israel’s aid and wrote the Secretary General of the United Nations Ban Ki-moon, demanding that the UN stop Hezbollah from rearming. The letter accused the UN of failing to enforce resolutions, including one that requires the “disbanding and disarmament of all Lebanese and non-Lebanese militias.”

“The violence in the area caused by Hezbollah is horrific, and it results from the failure of the United Nations to enforce Security Council Resolutions 1559 and 1701,” the lawmakers wrote.

The case for preventive military action against Hezbollah was recently made by Ambassador Dore Gold, who is considered close to Netanyahu and was just appointed director general of the Israeli Foreign Ministry. Accusing the UN of having failed to stop Hezbollah, Gold argues that “Either the IDF will have to destroy the weapons now being stored in southern Lebanon, or let Hezbollah fire thousands of rockets into Israel. What would you do?”

Hezbollah already seems overextended due to its involvement in the Syria conflict, and it could ill afford a war with Israel at this time. Nonetheless, if Israel attacks Lebanon, it is difficult to imagine Hezbollah not responding, despite its difficulties in Syria and despite the impact it may have on the ongoing Iran talks.

General Yahya Rahim Safavi, military adviser to Iran’s supreme leader Ayatollah Ali Khamenei, warned on May 21 that any Israeli attack would unleash a firestorm of missiles on its cities “Iran, with the help of Hezbollah and its friends, is capable of destroying Tel Aviv and Haifa in case of military aggression on the part of the Zionists,” he said.

Clearly, if Israel and Hezbollah do go to war, killing the Iran agreement would not be the only motivation. But the prospect that such a war would greatly support the rhetoric of those in the United States arguing against the deal with Iran would certainly be a major consideration in the minds of Israeli policymakers. The temptation of being able to kill the Iran agreement may become the deciding factor in Israel’s decision-making.

If so, it wouldn’t be the first time that an Israeli confrontation with Hezbollah would be motivated by a belief (or desire) that war with Iran was looming. In the midst of the Israeli-Lebanese war in 2006, Israel’s then-Deputy Defense Minister Ephraim Sneh said Lebanon was all about Iran. ” War with Iran is inevitable. Lebanon is just a prelude to the greater war with Iran,” he commented.

Sneh was wrong. War with Iran neither was nor is inevitable. But a war with Hezbollah this summer can help Israel make sure that peace with Iran is beyond Obama’s reach.