Hezbollah leader Sheikh Hassan Nasrallah has warned Israel of launching new attacks against his Lebanon-based Shia Muslim group.
His speech was broadcast at a mass rally in Beirut to mark the first anniversary of the end of the war between Hezbollah and Israel.
Hezbollah regards the 34-day war as a "divine victory" for its forces.
More than 1,000 Lebanese, mostly civilians, died in the war as well as 116 Israeli soldiers and 43 civilians.
"If you, the Zionists, are considering attacking Lebanon, I am reserving a surprise for you that will change the fate of the war and the region," Sheikh Nasrallah told thousands of people attending the rally.
"In the same way we were victorious in August 2006, I warn them that here in Lebanon there is A resistance, an army and a people... that reject humiliation and fear only God," he said.
He added that Israel and the US had tried to divide the Lebanese people during the war.
Sheikh Hassan Nasrallah did not personally attend the gathering, which was organised by Hezbollah. His speech was broadcast on giant TV screens set up at the venue.
Much of Lebanon's infrastructure was damaged by an intense Israeli bombardment in 2006 after Hezbollah forces seized two Israeli soldiers in a cross-border raid
Bridges, roads and thousands of homes were destroyed in the Israeli bombardment and a major ground assault across the border.
Israeli Prime Minister Ehud Olmert has faced repeated calls to resign over his handling of the war.
One of Israel's stated aims was to eliminate Hezbollah's ability to fire rockets, thousands of which were launched into northern Israel.
Despite its military weight, Israel was unable to crush Hezbollah, allowing the group to claim victory.
The two Israeli soldiers remain captive.
UN Security Council resolution 1701 halted the war, allowing for the deployment of Lebanese soldiers and a beefed-up UN peacekeeping force to the battle zone along the southern border with Israel - Hezbollah's stronghold
An uneasy peace has existed in the last year but Hezbollah has not disarmed - one of the conditions of the UN Security Council resolution.
Lebanon is now facing its biggest political crisis since the end of its long civil war in 1990.
It is trapped between those in the government who look to the West and those in the opposition who look to Syria, says the BBC's Christian Fraser in Beirut.
The French foreign minister, Bernard Kouchner, is attempting to mediate between the two sides.
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