The head of Lebanon's Hezbollah vowed Tuesday his terrorist group would oust Sunni rebels from a region on the border with Syria, but declined to say when the assault might happen.
In a televised address, the Shia Islamist group's leader Hassan Nasrallah said rebel forces in the mountainous border area posed an unacceptable threat to Lebanon's security.
"This issue needs radical treatment. We are talking about a real aggression that exists and is present," Nasrallah said of the rebels in the Qalamoun area.
"The (Lebanese) state is not able to address this issue... so we will proceed with the necessary treatment and assume the responsibility and consequences."
The Qalamoun region straddles the Syria-Lebanon border and 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 - including Sunni jihadists - remain entrenched in the mountainous area that runs directly along the border, which is porous and ill-defined.
From there, jihadists have launched attacks inside Lebanon, including in August 2014, when fighters from Al Qaeda's Syria affiliate Al Nusra Front and the Islamic State group briefly overran the eastern Lebanese town of Arsal.
A truce ended the attack, but the groups took several dozen Lebanese security forces with them as hostages when they withdrew from the town into the surrounding mountains.
They have since executed four of them, and Al Nusra on Tuesday released a video showing some of the remaining 25 hostages warning they would pay the price of any operation in Qalamoun.
Speculation has been rife about a spring attack in Qalamoun by Hezbollah, which has bolstered Syrian President Bashar al-Assad against rebels in battles throughout the country.
On Monday, Islamist rebels led by Al Nusra launched a preemptive attack against Hezbollah positions in the region, and a source close to the Al Qaeda affiliate said "the battle in the region has begun".
But Nasrallah declined to say when Hezbollah would launch any major operation in the area.
"There are preparations, and people are seeing that and speculating about it," he said.
"But we haven't announced anything official... and even when we start, we will not issue a statement," he added.
"When we begin, the operation will speak for itself."
Hezbollah has been a key force multiplier for Assad as he has battled an uprising that began with anti-government protests in March 2011 and spiraled into bloody civil a war after a regime crackdown.
Last Thursday, Nasrallah reaffirmed his group's full commitment to defending the Assad regime, telling a senior Lebanese politician that "President Assad and his government cannot fall as it would also mean the fall of Hezbollah and the axis of resistance"
But the group's involvement has worsened existing sectarian tensions in fragile Lebanon, which fought a civil war between 1975 and 1990.
The country's Shia population largely backs Hezbollah and the Syrian regime, while Lebanon's Sunnis have broadly supported the Sunni-led uprising against Assad.
Earlier Tuesday, former prime minister Saad Hariri, who heads Lebanon's anti-Hezbollah bloc, warned against any operation in Qalamoun, suggesting it could threaten the country's security and the lives of the security forces being held hostage.
Syria's conflict has regularly spilled into Lebanon in the form of battles along the border and bombings against Hezbollah strongholds, and the country is hosting more than 1.1 million Syrian refugees.
AFP contributed to this report.