"If there is movement towards peace in the region, then Hezbollah has a problem," he added. "If there's movement toward war, Hezbollah has a problem. And now if the tribunal moves forward, they will also have a problem."
Oussama Safa, who heads the Lebanese Centre for Policy Studies, estimates Lebanon has a "50-50 chance" of descending into yet another round of violence in the light of Nasrallah's surprise announcement late on Thursday.
In a rare press conference, the Shiite leader said Prime Minister Saad Hariri, son of the slain ex-premier, had informed him months ago that Hezbollah members would be accused by the STL.
He said Hariri had also assured him that he would publicly avow that it was "undisciplined" Hezbollah members, and not the party itself, who were implicated.
"The country could go towards a confrontation and it could also go towards a way to contain this -- certainly not by stopping the indictment," Safa told AFP. "But I think all parties have an interest in containing this."
Politicians and judges, including STL president Antonio Cassese, have said they expect an indictment by the end of the year, sparking fears of a repeat of the violence in May 2008 that brought Lebanon close to a new civil war.
More than 100 people were killed that month when Hezbollah staged a spectacular takeover of mainly Sunni west Beirut following a crackdown on the party.
Omar Nashabe, a specialist in criminal justice and columnist with Lebanese daily Al-Akhbar, said Nasrallah's speech on Thursday was a well-timed wake-up call.
"He is calling for a revision ... by the group that chose the wrong path by accusing Syria, and now that same group is moving toward Syria," Nashabe said, referring to Hariri's Western- and Saudi-backed alliance.
"They should think carefully if they want to accuse Hezbollah to avoid repeating the same mistake as with Syria," he added.
Hariri had initially accused Syria of the February 14, 2005 Beirut bombing that killed his father and 22 others, forcing the pullout of Syrian troops from Lebanon after a 29-year presence.
But his relations with Damascus, which has consistently denied involvement in the murder, have warmed and he has visited Syria four times in the past eight months.
"At a time when Hezbollah feels under attack and Nasrallah is making these statements, Hariri is in Syria meeting and making agreements and I think Hezbollah is wondering where Syria is going," Salem said.
Safa believes the newfound rapprochement bodes well for stability in Lebanon.
"I think the better Hariri's relationship with Syria gets, the more detente we will see and the more we are able to keep a lid on any violent reaction," he said.
Political blogger Elias Muhanna for his part says the commotion surrounding the UN tribunal's finding could well be a ploy to defuse tension.
"By the time that the STL gets around to indicting Hezbollah members a few months from now... the development will be old news, already dissected, analysed and picked over by Beirut’s punditocracy," Muhanna wrote on his blog Qifa Nabki.
"No one will be surprised and (if Nasrallah and others get their way), no one will really care."