In a televised address on the eve of an international conference in Rome designed to find a solution to the two-week-old conflict, Sayyed Hassan Nasrallah said Hezbollah would reject any deal that compromised Lebanon's sovereignty.
"We cannot accept any condition humiliating to our country, our people or our resistance," Nasrallah said.
Condoleezza Rice, the US secretary of state, had put forward peace proposals during a visit to the region this week. Lebanon's parliament speaker said these involved Hezbollah's withdrawal from the border and the deployment of an international force.
In the conflict, Hezbollah has hit Haifa, Israel's third-largest city 35km (20 miles) south of the border, with rockets for the first time.
"In the new period, our bombardment will not be limited to Haifa," Nasrallah said. "If matters develop, we will choose the time when we will move beyond, beyond Haifa."
Israel has launched an incursion into southern Lebanon against Hezbollah fighters.
"In the new period, our bombardment will not be limited to Haifa ... If matters develop, we will choose the time when we will move beyond, beyond Haifa"
Sayyed Hassan Nasrallah, the Hezbollah leader
"Whatever the incursion, it will not stop rocket fire into Israel," Nasrallah said.
He said that the Shia Muslim group would take back any land Israel occupied.
Nasrallah accused Israel of launching a psychological war to undermine Lebanese morale and of exaggerating casualties inflicted on Hezbollah.
"We do not hide our martyrs. If any of our leaders or ranks were killed, we announce that and take pride in that," he said.
Israel has said it plans to create a security zone in the south that it would keep until international forces arrive.
"Any coming of the Zionist army to our land will more enable us to damage its troops, officers and tanks," Nasrallah said.
Hezbollah attacks on Israeli forces helped to remove the Israeli army from south Lebanon in 2000 after 22 years of occupation.
"It will give us a wider and bigger chance for direct confrontation and to bleed the forces of this enemy," he said.
The US 'project'
Nasrallah said Israel had prepared to launch a war on Hezbollah and would have done so regardless of the group's capture of the soldiers. He said the United States wanted to wipe out Hezbollah as part of its plan for a new Middle East.
"In the view of the Americans, there are barriers to the new Middle East, meaning the area which the US administration controls"
"The project upon which the war was planned is the return of Lebanon to the sphere of American-Israeli control," he said.
"In the view of the Americans, there are barriers to the new Middle East, meaning the area which the US administration controls.
"The main barriers ... are the resistance movements in Palestine and Lebanon and at the level of governments, Syria and Iran." Both countries back Hezbollah.
"Therefore what is required [by the United States] is work to end these barriers and their removal by way of the historic American project being prepared for this region."