"We have been holding discussions for several days with Burhan Ghalioun; there are also Kurds and representatives of tribes," he said.
Ghalioun, a France-based academic, was recently designated leader of a rival opposition group, the National Transitional Council, which has Islamist and nationalist supporters.
"When the SNC meets, there will be a new assembly which will be expanded to these new movements," Khoja said, adding the meeting scheduled for Saturday would now not take place before Sunday at the earliest because of the negotiations.
According to diplomatic sources in Damascus, the rise of the SNC, founded on an accord between Washington, Ankara and the Muslim Brotherhood, could unite the nationalist, liberal and Islamist trends of the opposition.
At least seven people died Saturday, said the Syrian Observatory for Human Rights, reporting killings in Idlib province of northwest Syria, Homs in the centre of the country, and Rastan where government forces have faced deserters.
Five civilians and six soldiers were killed in clashes in Rastan on Friday, while the Observatory said two young men on Saturday died of injuries from gunshot wounds near the capital.
And the London-based rights group voiced concern over the life of a young activist, Anas al-Shougri, who was at the forefront of protests in the port city of Banias before his arrest in May.
The Local Coordination Committees group put Friday's death toll at 23.
The United Nations says 2,700 people have been killed in the protests against President Assad. The UN Security Council, meanwhile, remains divided over whether to threaten Assad's regime with sanctions over its deadly crackdown on dissent.
European nations on Friday dropped the word "sanctions" from a proposed resolution on Syria in a bid to temper Russian opposition.
France, Britain, Germany and Portugal instead called for "targeted measures" in their draft text. Russia and China have threatened to veto any resolution calling for punitive measures against Damascus.
On the ground, activists said those killed in Homs on Friday were shot dead by security forces, while around 250 tanks and armoured vehicles entered Rastan, a major city in the province and the scene of intense operations against army defectors.
"Five civilians and six military and security agents have been killed today in the village of Kafar Zita during clashes between soldiers and agents on one side and deserters on the other," the Syrian Observatory said.
"Eight civilians were killed Friday in Homs province" by fire from security forces, added the watchdog.
Much of the violence was in Rastan, about 180 kilometres (120 miles) from Damascus and a gateway to the north, where battles have raged since Tuesday between the army and deserters who refuse to fire on protesters.
The Observatory, citing a local activist, said an army officer was shot dead by pro-regime gunmen "for refusing to go to Rastan as ordered."
Activists also reported protests in other locations including 10,000 people in Palmyra (Tadmur) in central Syria, as well as thousands in Hama, also in the centre, Idlib, and Zabadani just north of Damascus.
The office of the UN High Commissioner for Human Rights in Geneva has said the death toll from the bloody crackdown has risen to more than 2,700 since March 15.