For the past four years, the Lebanese militant group Hezbollah has fought a war in Syria, supported Iraqi forces and stage-managed the politics of its homeland, all the while trying to avoid facing off with Israel. Yet its exhausted leaders fear the last gasps of Donald Trump’s presidency could deliver threats that eclipse everything else.

In the organisation’s heartland, Hezbollah members are watching the clock – and the skies. Israeli jets have been streaking overhead for more than a month, and over the past few weeks the frequency of flights has sharply increased, as has security in Beirut’s southern suburbs, the nerve centre of the region’s most powerful militant group.

Leaders and senior members fear that Trump, his outgoing secretary of state, Mike Pompeo, and Israel intend to use the weeks before Joe Biden’s inauguration to act decisively against Iran and Hezbollah before the new president takes a widely anticipated softer stance.

“They’ve got their window and they want to finish what they started, said one mid-ranking Hezbollah group. “But don’t worry, the Sayyid [the group’s leader, Hassan Nasrallah] is safe.”

Interviews with two mid-ranking Hezbollah members and an intermediary familiar with the thinking of the group’s most senior leaders have revealed a picture of an organisation determined not to be drawn into a clash with Israel or to be seen as explicitly acting in defence of Iran. All three sources said they believed the incoming US administration would attempt to negotiate the nuclear deal with Tehran, which was inked by Barack Obama and revoked by Trump and could now be renewed in another incarnation.

“That means sanctions relief, and that means that the pressure will eventually be off us,” said one of the Hezbollah members. “They are trying to hurt Iran to damage us. It won’t work because everybody has seen this plan since the summer. And we all have the means to survive their pressure.”

Israeli attacks on Iranian targets inside Syria have been a near weekly occurrence since early 2017, and Hezbollah members, who have been heavily involved in shoring up the Syrian leader, Bashar al-Assad, have sometimes been killed in airstrikes, though its senior members have not recently been targeted. The killing of Iran’s chief nuclear scientist, Mohsen Fakhrizadeh, outside Tehran on 27 November, almost certainly by Israel, has stirred alarm in Beirut that the distinction so far drawn between Iran and Hezbollah may change in the next month and a half.

One senior figure described the coming weeks as “the most dangerous period for the last 30 years. Everyone is worried, and with good reason.”

So far Israel has indicated that the ranks of its arch foe are not its prime target in Syria and has at times fired warning shots at targets it knows to include Hezbollah members, to avoid killing them. One such attack, in April, involved a missile landing near a Jeep at the border crossing from Syria to Lebanon. When four Hezbollah members fled the vehicle, a second missile destroyed it.

Israeli leaders have heavily backed the US policy of “maximum pressure” on Iran and Trump’s revocation of the nuclear deal, and seen both as prime opportunities to diminish Hezbollah, which it views as a potent and growing threat, emboldened by chaos in Iraq and Syria.

The alignment of Israeli interests with a Saudi Arabian and Gulf worldview on Iran has been championed by Trump officials as a prime reason for normalisation deals struck with the UAE and Bahrain and for warming ties with Riyadh.

Israeli leaders believe their counterparts in the Gulf to be as hostile towards Hezbollah and Iran as they are, and are unwilling to bail out Lebanon from its catastrophic economic collapse for as long as the group maintains a grip on the country’s politics.

“It doesn’t matter at all what the Saudis say,” said a second Hezbollah member. “The party can look after its own. They must understand that if the country falls, who will emerge the strongest? It won’t be the parties that they support.

“But will they try something big in Beirut in the coming weeks? It’s possible and it’s true there are security alerts in Dahiyeh and in the south. This is all about protecting our leaders. We don’t have anything specific. But there is something in the atmosphere.”

Hezbollah’s security zone in the heart of its stronghold is ringed with steel barriers that were lifted last week, allowing cars to pass. Security members stood on roadsides observing the flow of traffic under the watch of large cameras that maintain an interconnected view of Dahiyeh.

Banners of the Iranian general Qassem Suleimani, who was assassinated in Baghdad on 3 January in a US drone strike, have been placed near intersections and hang from shopfronts all throughout Dahiyeh, and photographs of Nasrallah are also prominent. Dogeared posters of lesser figures killed in Syria and Iraq and in earlier clashes with Israel are also common.

“We don’t fear death, as you know,” said the second Hezbollah member. “But we must protect our leaders and we know that we would be damaged politically if anything happened to them. These are dangerous times. Trump is crazy, but he won’t get what he wants. He doesn’t have patience and he doesn’t have time. The Israelis think they’re coming for us. We’re the ones coming for them.”