In a televised address the Lebanese Shia-Muslim movement's leader said rebel forces in the area posed an unacceptable threat to Lebanon's security.
But he refused to say when the assault might take place.
The region in question, Qalamun, was a stronghold of rebel forces until a major operation by Syrian regime troops backed by Hezbollah fighters last year.
While most of the region was recaptured, opposition fighters and jihadists remain entrenched in the mountainous area that runs directly along the border, which is porous and ill-defined.
“The concern for groups like Hezbollah is that these militants will infiltrate from Syria into Lebanon and launch an attack,” explains Julien Barnes-Dacey, a senior policy fellow at the European Council on Foreign Relations. “We saw a series of those where militants were able to get into Beirut, targeting areas where Hezbollah is present.”
The al-Qaeda linked al-Nusra Front and the Islamic State armed group have launched attacks into Lebanon from Qalamun.
In August 2014 al-Nusra fighters briefly overran the eastern Lebanese town of Arsal.
The armed group also currently are holding 25 members of the Lebanese security forces hostage.
“But there is also the fear that, from Hezbollah perspective, that these groups will mobilise Sunni in the north of the country,” says Barnes-Dacey. “And that they actually create a broader momentum of Sunni jihadist opposition which would push more aggressively against Hezbollah in Lebanon and could propel the country into its own spiral of violence.”
Speculation has been rife about a spring attack in Qalamun by Hezbollah and on Monday Islamist rebels led by Al-Nusra launched an attack against its positions in the region.
The armed groups are becoming more powerful, says Mario Abou-Zeib, an analyst with the Carnegie Institute in Beirut.
“In the past two months we witnessed an amazing development of those militants, whether on the logistical level or the manpower level, which led to the creation of what is basically an army” he notes. “It is basically an alliance between all the factions existing in the mountains, with the exception of the Islamic State.”
But those hoping for a fast victory might be disappointed, warns Abou-Zeid.
“From a logistical perspective, a fast victory will not be possible," he told RFI. "Those militants are very well established in the Qalamun mountains and they occupy much more advanced positions than Hezbollah and the Syrian regime, on both side of the border.”
Earlier yesterday, former Prime minister Saad Hariri, who heads Lebanon's anti-Hezbollah bloc, warned against any operation in Qalamun.
Hariri suggested it could threaten the country's security and the lives of the hostages.
But, as Mario Abou Zeid explained, a victory is vital for Hezbollah.
“If they lose this battle, their supply of arms from the Syrian border will be put under additional pressure, which Hezbollah cannot tolerate at the present time” he said. “They're mobilising to the extreme and putting everything they’ve got into this fight. This will not be a short fight, it’s going to be lengthy and costly.”
A victory could nonetheless help the Syrian’s government.
Hezbollah is a key ally of Bashar al Assad's regime and it has been fighting alongside the Syrian government since 2012.
On Monday Hezbollah captured a Syrian village close to the border.
“They have been a very active partner of the Assad’s regime in fighting the opposition” says Barnes-Dacey. “They’ve put considerable numbers of fighters on the ground in Syria since 2012, certainly the regime has come to depend on them quite extensively.”
Assad knows that if he loses Hezbollah's support his only remaining ally will be Iran.