JERUSALEM — With Lebanon in turmoil and a Hezbollah-backed prime minister poised to take power in Beirut, Israel is concerned at the prospect of a tectonic shift in the regional balance.

For the moment, however, Israeli officials do not expect Lebanon’s political turmoil to trigger a new round of fighting on the Israel-Lebanon border.

The primary strategic concern of Hezbollah’s ascent is the potential spread and strengthening of Iranian influence in the region. The so-called Shiite Crescent stretches from Tehran to Shiite-ruled Iraq, through Shiite-friendly Syria and into Lebanon, where Hezbollah, Iran’s Shiite proxy, is now in power. This extension of Iran’s influence poses a serious threat to Israel from both the east and the north.

In Israel’s view, Hezbollah’s gambit — engineering the collapse of Saad Hariri’s pro-Western government and pulling the strings to get its own candidate, billionaire business tycoon Najib Mikati, in line to replace him — constitutes a significant step toward moving the moderate, majority Sunni-Christian country into the radical Shiite Iranian orbit.

“The situation in Lebanon is dangerous. Hezbollah is not just another terrorist organization. It is a terrorist organization in control of a country,” Silvan Shalom, Israel’s minister for regional cooperation, said on Israel Radio on Wednesday. “The international community should do everything it can to prevent a situation in which Lebanon becomes a hostage to Hezbollah and Iran.”

Israeli analysts see a common denominator in the current regional turbulence in Tunisia, Egypt and Lebanon. In all three cases, they say, radical, potentially pro-Iranian forces are making inroads at the expense of more moderate Sunni regimes. In other words, in the grand regional power struggle between the Iranian radicals and the Egyptian and Saudi-led moderates, the Iranians are making significant gains.

Despite the high strategic stakes and the volatility of the situation, Israeli officials do not expect another round of fighting between Hezbollah and the Israel Defense Forces at this stage.

The Israeli military intelligence estimate is that Hezbollah, still smarting from the effects of the 2006 Lebanon War, does not want another cross-border confrontation — just yet.

Nor, for that matter, does Israel. Indeed, as part of the effort not to exacerbate tensions, the IDF has been careful not to move troops to the northern border.

“We want the northern border to remain quiet, and we will not give anyone on the other side an excuse to heighten border tensions,” a senior Israeli official told JTA on condition of anonymity.

Hezbollah prefers to pull the strings from behind the scenes, Military Intelligence Chief Maj. General Aviv Kochavi told the Knesset’s Foreign Affairs and Defense Committee on Tuesday. Hezbollah fears that formally taking over Lebanon might weaken the movement by making Lebanon vulnerable to sanctions and attack, like Hamas in Gaza. Both Hamas and Hezbollah are considered terrorist groups by Israel, the United States and some European countries.

Indeed, Hezbollah leader Sheik Hassan Nasrallah was careful not to appear to have seized power in Lebanon.

“Hezbollah will not lead the next Lebanon government,” Nasrallah said on Tuesday. “Najib Mikati,” Hezbollah’s designate for prime minister, “is not a Hezbollah man,” Nasrallah said.

So, to what extent is Hezbollah really in charge?

Although put forward by Hezbollah, Mikati actually is closer to Syria than to Hezbollah or Iran. He, too, has been at pains to distance himself from his Shiite patrons.

“Don’t prejudge me or my behavior, please, especially in the international community,” he said in an interview with the French News Agency AFP.

Like Hezbollah, Mikati is all too aware that his being perceived as a Hezbollah puppet could have serious economic and diplomatic consequences for Lebanon. In protesting his independence, he was responding to a blunt warning from U.S. Secretary of State Hillary Clinton.

“A Hezbollah-controlled government would clearly have an impact on our bilateral relationship with Lebanon,” Clinton said in Washington on Tuesday. The United States has delivered $1.2 billion in economic and military assistance to Lebanon over past five years; another $246 million in the pipeline is now in doubt.

Much will depend on how Mikati handles his first real test on Feb. 7, when the international court at The Hague is presented with the findings of the UN-backed Special Tribunal on Lebanon. The findings reportedly blame Hezbollah for the February 2005 assassination of Saad Hariri’s father, former Lebanese Prime Minister Rafiq Hariri.

Mikati owes his elevation to the premiership to Saad Hariri’s refusal to repudiate the tribunal’s findings. That stance led to the collapse of Hariri’s government on Jan. 12 when 11 Hezbollah-backed Shiite ministers resigned en masse, sparking the current political crisis.

Now Mikati’s Hezbollah patrons will expect him to deliver where Hariri would not. This puts the new Lebanese leader on the spot. If he repudiates the tribunal’s findings, the international community will see him as a Hezbollah puppet; if he doesn’t, he almost certainly will lose his job.

However the current crisis plays out, for Israel the prospect of a future showdown with Hezbollah, as part of the regional struggle for hegemony with Iran, remains as high on its threat map as ever, if not higher.

In the Israeli estimate, Hezbollah already has approximately 45,000 rockets and longe-range missiles, more than four times the arsenal it had before the Lebanon war of 2006. Israel also says Hezbollah has built hundreds of outposts and bunkers south of the Litani River — in blatant violation of UN Security Council Resolution 1701, which brought the hostilities in 2006 to an end.

When in a recent tripartite meeting of IDF officers, Lebanese army personnel and U.N. peacekeepers, the Lebanese denied claims that Hezbollah had been allowed to move to southern Lebanon below the Litani River, the Israeli officers produced detailed maps showing the precise location of the Hezbollah positions.

Neither the U.N. forces nor the Lebanese army has since done anything to challenge the resolution-violating Hezbollah deployment.

The big question, though, remains unanswered. Is there a red line that, if crossed by Hezbollah, would prompt Israel to intervene in Lebanon? That’s an issue no one in the Israeli establishment is prepared to address publicly.