Naim Kassem, number two in the Iranian-backed Lebanese group "Hezbollah", spoke after Defense Minister Yoav Galant said that Israel is determined to restore security on its northern front, France24 reports, quoted by FOCUS.
Last week, Gallant told Israeli troops that "we are preparing for anything that could happen in the north".
In his speech in Beirut, Qassem stated: "We have no intention of going to war, as we believe it would not be useful.
"However, if Israel unleashes a war, we will confront it - and there will be heavy losses on both sides,", he notes.
"If they think that such a war will allow 100,000 displaced people to return to their homes ... we issue this warning: prepare to deal with hundreds of thousands more displaced people.“
"Hezbollah" has exchanged fire almost daily with Israeli forces in support of its ally Hamas since the Palestinian militant group's October 7 attack on Israel sparked a war in Gaza.
Thousands of people living in the border area of the two countries have been displaced by the fighting.
According to AFP data, as a result of the cross-border violence since the beginning of October, 623 people have died in Lebanon, mostly fighters, but also at least 142 civilians.
On the Israeli side, including in the annexed Golan Heights, authorities announced the deaths of at least 24 soldiers and 26 civilians.
On Saturday (September 14), Qassem said of the displaced in Israel: "It is impossible to bring them back, regardless of the sacrifices that have been made.
"So take your time and think before you make a decision. We are prepared for any possibility."
In late August, the Israeli military said it had foiled a major Hezbollah attack aimed at avenging a military commander killed in an Israeli airstrike near Beirut.
Israel said it had destroyed "thousands" Hezbollah rocket launchers, while the Lebanese group insisted it had shelled the border with drones and rockets.
This was perhaps the largest exchange of fire between Israel and "Hezbollah" since the beginning of the war in Gaza.
However, violence has since subsided, with analysts saying both sides want to avoid a wider regional flare-up.