The leader of the al-Qaeda-linked rebel group fighting in Syria denounced efforts in Saudi Arabia to unify Syrian opposition groups saying those involved in talks were committing "treason".

In an interview with several media groups, including Al Jazeera, al-Nusra Front's leader Abu Mohammed al-Joulani said the Riyadh conference was part of a "conspiracy" to revive and sustain the regime of President Bashar al-Assad.

"The conference was not organised to help the people of Syria," Joulani said

He said al-Nusra Front was not invited to attend the talks, and it wouldn't have shown up even if it had been asked.

Other armed groups attending had committed "treason to the sacrifices made by the Syrian people" in the nearly five-year-old civil war, Joulani said.

 Lebanese army conducts prisoner swap with Syria's al-Nusra Front

The Saudi meeting came after diplomats from 17 countries - including backers and opponents of Assad's government - agreed last month in Vienna on a road map for the Syrian conflict.

This would see a transitional government set up within six months and elections within 18 months, along with negotiations between the opposition and the Syrian regime by January 1.

Joulani ruled out any chances of a truce or political settlement with the Assad government, adding Syrian forces only control about 20 percent of the country's territory.

"As far as we are concerned, the regime is all but finished … and in fact it has become more factions than a regime, controlled by this colonel or that general," said Joulani.

More than 250,000 people have been killed and millions forced from their homes since the Syrian conflict erupted in March 2011 with anti-government protests.

After launching military action in September, Russia has so far failed to make any significant advances and will fail in propping up the Syrian government, said Joulani.

He also stressed that al-Nusra Front has no intention of operating against anybody outside of Syria. He said his group will never see eye to eye with the West because of its commitment to uphold "Islamic justice".

Joulani also defended his organisation's relationship with al-Qaeda, praising it for defeating "the West's designs against Muslims in Afghanistan and Iraq".

Ali Younes contributed to this report

Source: Al Jazeera and agencies