Lebanon's Hezbollah movement said Friday it would be "fully prepared" to join its Palestinian ally Hamas in the war against Israel when the time is right.
Hezbollah deputy chief Naim Qassem spoke as Hamas and Israel traded heavy fire for a seventh day, after the Hamas attack.
Israel has retaliated by bombarding Hamas targets in the Gaza Strip, killing some 1,800 people.
"We, as Hezbollah, are contributing to the confrontation and will (continue) to contribute to it within our vision and plan," Qassem told a pro-Palestinian rally in Beirut's southern suburbs.
"We are fully prepared, and when the time comes for action, we will take it," he said.
The official, whose remarks coincided with a visit to Beirut by Iran's foreign minister, rebuffed calls for Hezbollah to stay out of the war.
Outreach by "major countries, Arab countries, and envoys from the United Nations, directly and indirectly, asking us not to interfere in the battle, will not affect us", he said, adding: "Hezbollah knows its duties."
Israel has traded fire with Hezbollah and allied Palestinian factions in Lebanon in recent days, although the tit-for-tat attacks have remained limited.
In Beirut's southern suburbs on Friday, more than 1,000 Hezbollah supporters rallied for Gaza, carrying Palestinian flags and banners that read: "May God protect you".
"(Hassan) Nasrallah, strike Tel Aviv," they chanted, addressing the leader of the Shiite Muslim group.
Najwa Ali, a Palestinian refugee born in Beirut 57 years ago, was among those taking part in the solidarity rally.
"I have never seen Palestine, but when I go back one day, it will be with my head held high, without an Israeli soldier telling me where to go or what to do," she told AFP.
On Monday, Hezbollah said Israeli strikes killed three of its members, while Palestinian fighters claimed a thwarted infiltration bid.
On Tuesday, Israel said it hit Hezbollah observation posts, while Hamas's armed wing claimed rocket fire.
On Wednesday, Hezbollah said it targeted an Israeli position near the Lebanese village of Dhayra. Retaliatory Israeli fire wounded three people.