Iran-backed Hezbollah is determined not to ramp up its monthslong firefight over Lebanon’s southern border, but will respond in kind to any Israeli escalation, the political party and militia’s second-in-command told NBC News in a rare and exclusive interview.

Naim Qassem faulted Israel and the United States for perpetuating tit-for-tat attacks that have killed hundreds in southern Lebanon and displaced tens of thousands of civilians on both sides of the Israeli-Lebanese border. The conflict started with Hamas’ terror attack on Israel on Oct. 7, which killed more than 1,200 people and sparked Israel’s bloody incursion into the Gaza Strip that has since killed nearly 34,000 people, according to the Ministry of Health in Hamas-ruled Gaza.

“We didn’t expect the war would last this long because we didn’t think that Netanyahu was that foolish, same for Biden and the other countries,” Qassem said, as Israel’s two-front conflict drags into its seventh month.

As Hezbollah’s deputy secretary-general, Qassem ranks second behind the group’s revered leader, Hassan Nasrallah.

Qassem’s comments came as Israel prepares its response to an unprecedented retaliatory Iranian missile and drone barrage against the Jewish state — an impending reprisal that would bring the Middle East closer to a region-wide war than at any time in recent memory.

But the latest round of fighting between Israel and Hezbollah began months before last weekend’s direct confrontation between Israel and Iran. Hezbollah is estimated to have upward of 150,000 rockets and missiles, in addition to drones and anti-tank, anti-aircraft and anti-ship missiles, according to a Reuters report, citing data from the CIA.

Hezbollah, a powerful, Iran-backed Shia political party and militant organization, was formed in the early 1980s during the Lebanese civil war and was an active force during the Israeli occupation of southern Lebanon, when it set a mission to expel Israeli forces from the country. The group has long claimed solidarity with the Palestinian cause. The U.S. considers Hezbollah a terrorist organization.

Hezbollah first struck a disputed border region of northern Israel on Oct. 8, the day after Hamas’ attack on Israel. At the time, Hezbollah called that strike an act of “solidarity” with Hamas. Iran also has backed Hamas for years.

Hezbollah claimed responsibility Wednesday for a missile and drone attack on northern Israel that injured 18 people, 14 of whom were Israeli soldiers, saying the strikes were retaliation for Israel killing two of the group’s commanders in a cross-border attack the day before.

Among the multiple Iran-backed groups that oppose Israel in the Middle East, Hezbollah is by far the strongest and the largest beneficiary of Iranian largesse.

Iran has declared that its attack Saturday night, which saw it launch more than 300 missiles and drones at Israel, marked the full extent of its retaliation for an April 1 strike by Israel on the Iranian Consulate in Syria’s capital, Damascus, that killed two senior commanders and five advisers from Iran’s Islamic Revolutionary Guard Corps.

Qassem said Iran repeated its public messaging to Hezbollah.

“Tehran speaks publicly and clearly. They do not want war and they have responded to the attack on their embassy and that’s it for them,” Qassem said. “I think Iran is honest. This is what they told us and this is what they keep reiterating to the media.”

Qassem offered measured criticism of the three Arab countries — Jordan, Saudi Arabia and the United Arab Emirates — that assisted in Israel’s defense against the Iranian salvo Saturday night.

“It wasn’t adequate for any Arab nation to support Israel no matter what justifications they had,” he said. “Their populations will hold them accountable for all those who took this decision.”

Qassem laid equal blame for the civilian losses in Gaza on both Israel and the United States, dismissing a recent public rift between U.S. President Joe Biden and Israeli Prime Minister Benjamin Netanyahu as little more than cosmetic politics meant to “safeguard America’s image.”

“I consider that Biden and Netanyahu are both complicit in one scheme with very minor differences,” Qassem said.

In an earlier interview in November, Qassem told NBC News that Hezbollah would push more forcefully into its fight with Israel if the Jewish state continued its incursion into Gaza.

But nearly six months later, both Hezbollah and Israel have mostly hewed to “rules of engagement” — an unstated understanding between both sides that has so far tempered the fighting and confined it to the two states’ border regions.

“We will not accept that the Israelis transgress the rules of engagement that are currently set in the south” of Lebanon, he said. “If the Israelis increase their attacks, we will increase our attacks as well.”

While Israel is playing by the rules of engagement for now, senior Israeli officials have threatened to destroy Lebanon if Hezbollah escalates.

In January, an assassination by drone strike in Beirut of a Hamas leader was believed to have been carried out by Israel, ratcheting up tensions then, though Israel did not claim responsibility.

Despite its limited engagement, Qassem said Hezbollah’s fight is “serving its purpose” by “luring the Israeli forces to get busy in the north,” referring to their shared border, rather than Gaza, which borders southern Israel.

“Therefore, we will continue to do so, and we will not wage a full-scale war unless the Israelis decide to get into war against us,” he said. “Then we are ready for the full confrontation.”

Israel and Hezbollah: Fears of escalation after flurry of attacks

Israeli soldiers were wounded when a building they were in was hit in a Hezbollah attack.

Cross-border fighting between Israeli forces and the Lebanese group Hezbollah have intensified in recent days, raising fears of a further escalation.

Hezbollah announced on Thursday the deaths of two fighters, after the Israeli military said it had struck sites in southern and eastern Lebanon.

On Wednesday, 14 Israeli soldiers were wounded in a missile and drone attack.

Hezbollah claimed it was a response to strikes a day earlier that the Israeli military said killed two commanders.

There have been exchanges of fire almost every day since the day after the start of the war between Israel and Hamas in Gaza in October. Hezbollah has said it is acting in support of the Palestinian group. Both are backed by Iran and proscribed as terrorist organisations by Israel, the UK and other countries.

More than 330 people have been killed in Lebanon, including at least 66 civilians, according to Lebanese authorities and the UN, while the Israeli military says 10 soldiers and eight civilians have been killed in Israel.

The hostilities have also displaced tens of thousands of people from border communities in northern Israel and southern Lebanon.

On Thursday morning, Hezbollah's media office put out statements saying that two fighters had been "martyred on the road to Jerusalem" - a phrase it has been using to refer to fighters killed by Israeli fire. It named them as Mohammed Jamil al-Shami and Ali Ahmed Hamada but provided no further details.

Lebanon's state-run National News Agency reported that two people had been killed in an Israeli drone strike in the border village Kfarkela at dawn.

Warplanes had also targeted the nearby village of Khiam with "six strikes and more than 100 artillery and phosphorus shells", it said.

The Israel Defense Forces (IDF) said in a statement that its aircraft had "eliminated two Hezbollah terrorists identified in the area or Kfarkela" overnight.

Fighter jets meanwhile "struck Hezbollah terror targets" in area of Khiam, including infrastructure and military structures, it added. Soldiers also "fired in order to remove an imminent threat" there, according to the statement.

On Wednesday evening, the IDF said jets had struck "significant Hezbollah terrorist infrastructure" used by the group's aerial defence system in northern Baalbek, which is in the Bekaa valley in eastern Lebanon.

That came hours after Hezbollah claimed it had carried out an attack that the IDF said injured 14 soldiers, six of them seriously and two moderately.

A number of anti-tank missiles and explosive drones were launched from Lebanese territory towards the Israeli border village of Arab al-Aramshe, according to the IDF.

Israel's Haaretz newspaper reported that the attack saw the anti-tank missiles hit a community centre in the Arab Bedouin community and nearby cars, followed by the incursion of two drones, one of which exploded on impact.

It said one of the injured soldiers was in a critical condition and that two members of an emergency response squad and three civilians were also hurt.

The IDF said it struck the sources of the fire, as well as Hezbollah military compounds and infrastructure in the Lebanese towns of Naqoura and Yarine.

Hezbollah said what it had targeted was the headquarters of an Israeli military reconnaissance unit in response to "the enemy's assassination of a number of resistance fighters in Ain Baal and Chehabiyeh".

The IDF said on Tuesday that its aircraft had carried out strikes in those areas which killed Ismail Youssef Baaz, who it said was the commander of Hezbollah's coastal sector in Ain Baal, and Mohammed Hussein Mustafa Shehoury, who it said was the commander of the rockets and missiles unit in the western region for the elite Radwan Force.

A member of that unit, Mahmoud Fadlullah, was killed alongside Shehoury, it added.

While Hezbollah confirmed the deaths of the three men, it did not identify Baaz or Shehoury as commanders.

Fears are growing that the cross-border hostilities will escalate into a wider regional war, particularly after Hezbollah's backer Iran launched more than 300 drones and missiles at Israel over the weekend in retaliation for a deadly strike on the Iranian consulate in Syria earlier this month.

The IDF said 99% of the drones and missiles were shot down by its forces, Western allies and Arab partners, and that an airbase in southern Israel sustained only minor damage when it was hit by four missiles. A young Bedouin girl was injured by shrapnel.

Dozens of rockets were also fired from Lebanon at northern Israel during the attack, while launches were also carried out from Iraq and Yemen, where Iran-backed armed groups operate.

Israel vowed to respond to Iran's unprecedented direct attack, but Western powers have urged restraint.

Hezbollah leader warns Israel will pay 'a high price' if Iran is attacked