Hassan Nasrallah spoke by video-link
The head of the Lebanese Shia movement, Hezbollah, has set out a new manifesto for the party.
In a televised speech Hassan Nasrallah focused on the group's armed confrontation with Israel, saying negotiations would not bring peace.
"The Israeli threat calls for a defence strategy built on popular resistance to defend against aggression," he said.
Hezbollah and its allies hold 10 seats in Lebanon's 30-member unity government formed by Prime Minister Saad Hariri.
The speech took place from an undisclosed location as Sheik Nasrallah fears Israeli assassination.
The AFP news agency reported him saying he would increase Hezbollah's military strength to stop Israel making the Lebanese suffer.
"The ongoing Israeli threat forces the resistance to continue to boost its capacity in order to fulfil its role in liberating occupied territory," he said.
The Hezbollah leader, who is backed by Iran and Syria, called for Lebanese political unity and the end to sectarianism, insisting Hezbollah and the Lebanese army had to resist Israel together.
The Lebanese unity government was only formed after five months of political deadlock that had threatened the country's stability.
Hezbollah's armed militia remains a divisive issue in parliament.
In May 2008 it deployed forces in parts of the Lebanese capital dominated by pro-government groups when political negotiations failed.
Hezbollah fought a war with Israel in 2006 during which more than 1,200 Lebanese, mostly civilians, were killed. Some 160 Israelis, most of whom were soldiers, also died.