In an interview in London during a two-day meeting of the NSF, Khaddam said that grass-roots opposition could topple President Bashar Al Assad's regime as have "people power" movements elsewhere in the world.
"In Syria, the people have had enough," Khaddam said.
"They are suffering from injustice, poverty, hunger, and the country's serious economic problems. There are millions of unemployed, there are hundreds of thousands of university and school graduates who can't find work related to their diplomas," Khaddam said.
The regime is afraid of the people's growing discontent, which is why it is using the security forces to arrest people, including writers and other intellectuals," the 73-year-old former vice-president said.
Khaddam said that the "rumble of disenchantment" against Assad could "turn rapidly into a popular movement, which leads to [his] fall".
The NSF's role is to channel such discontent into "civil disobedience and thus overthrow the regime peacefully", said the leading member of the NSF, which also includes the Muslim Brotherhood.
"We are not calling for violence ... We do not want the regime to be overthrown in a military coup, because we believe that coup d'etats have created many problems in Syria and other Arab countries," Khaddam said.
He said that the meeting in London aims to work out a plan of action for establishing a democratic government in Syria.
The NSF, he added, seeks to establish links with the various opposition movements that exist inside Syria in order to coordinate a movement for change.
"We will do it because we share the same goals and the same reasons for acting," he said, adding that there were no differences among the opposition.
"I'm convinced that the Syrian people will manage to change the regime and establish a modern state based democratic institutions designed by the people, and whose leaders will be elected by the people," he said.
Such a change should be based on the principle of changing leadership in a government that accepts not to have one person hold a monopoly of power, he said.
Khaddam said that the Syrian opposition movement wants the international community "not to cover up for the regime's mistakes and to help the Syrian people to handle this crisis to get rid of this corrupt and violent regime which has lost legitimacy at home and abroad".
The opposition, on the other hand, has a duty to explain what is going on internally to the international community so that it can better help the people to prepare a brighter future, he said.
About 50 opponents of the Assad regime, including Kurdish parties, independents and communists, are present at the London talks which were not, however, attended by opposition figures living in Syria.
The talks end on Monday.
© 2006 Agence France-Presse