At least 100 delegates from the political opposition and rebel factions - including hard-line Islamist groups - met in Riyadh on Wednesday for two days of talks meant to unify the divided Syrian opposition as the international community pushes a political solution to end the Syrian conflict.

At least 16 rebel factions are participating in the closed-door talks, including the powerful Islamist groups Army of Islam and Ahrar al-Sham, which has ties to the al-Qaeda-affiliated al-Nusra front.

The talks also include some 20 members of the Western-backed Syrian National Council and the Syrian-based National Coordination Body.

The Saudi effort aims to bridge the gap between Syrian opposition and rebels groups to develop a common platform and negotiating position, as well as form a negotiating team ahead of potential early January talks with representatives of the Assad regime.

The Riyadh talks come as the US, Russia, Turkey, Saudi Arabia, Iran and more than a dozen other countries that both support the opposition and regime agreed last month in Vienna to renewed a push for a political solution to the nearly 5-year-old war, which has killed at least 250,000 people and displaced some 12 million.

The renewed diplomacy gained urgency following the refugee crisis in Europe, the increasing threat of "Islamic State" and Russia's military intervention in Syria - backed by Iranian and Hezbollah militias - to bolster regime forces, an event which marked a significant escalation of a conflict.

None of the Syrian opposition and rebel factions was invited to Vienna, where the outline of peace talks was agreed upon that would see a transition government set up before elections being held in 18 months.

The talks left unresolved the role of Assad in a transition, a major sticking point among international powers and within the opposition.

Most of the Syrian opposition has called for Assad's ouster, potentially putting it at odds with Russia and some Western countries that have softened their stance that he must leave before a political transition.

The West's attention has been turned to fighting the Islamic State, and after five years of conflict even the US has come to the realization the Assad regime is likely to hold on to power and his sudden fall could usher in further chaos.

Role of Ahrar al-Sham

The US has approached the hardline Ahrar al-Sham with caution, neither discounting including the group in the future of Syria nor opening up to it.

US officials have indicated their position vis-à-vis the Salafist group would likely be determined by its relationship with al-Nusra and its ability to compromise and work with the broader Syrian opposition.

For its part, Russia has insisted international powers come up with a list of terrorist organizations - which would from Moscow's view include groups such as Ahrar al-Sham - and legitimate opposition to negotiate with the Syrian regime.

In a sign Ahrar al-Sham would not soften its stance, the group issued a statement on Wednesday setting numerous preconditions that are likely to be unpalatable by other moderate rebel factions and the West.

"We came to stress that we want to liberate all the territories under Russian and Iranian hegemony, to oust the regime of Syrian President Bashar al-Assad, to preserve the sovereignty of our country," the group said in the statement, adding "Islamic identity" should be preserved and regime figures brought to justice.

The group said it demanded the "overthrow of the Assad regime with all its pillars and symbols" including the military and security apparatus, as well as the "the complete cleansing of the Russian-Iranian occupation of Syrian land, and the sectarian militias which support it."

World powers in Vienna have agreed to keep state structures intact, fearful of a repeat of what occurred in Iraq could empower the "Islamic State" or lead to complete state collapse.

Ahrar al-Sham also rejected some groups as "closer to the (Syrian) regime than they are to the revolution."

Some Syrian opposition and rebels groups boycotted the Riyadh talks over Ahrar al-Sham's inclusion.

Kurds go their own way

Meanwhile, notably left uninvited to the Riyadh talks were the main Syrian Kurdish group, the Democratic Union Party (PYD), and its militia, the People's Protection Units (YPG).

The YPG recently formed a new US-backed group dubbed the Syrian Democratic Forces consisting of some Free Syrian Army units, Arab tribes and Assyrian Christians.

The Syrian Kurds have carved out autonomous zones in northeast Syria and been some of the best fighters against IS. They have also clashed with al-Nusra, Ahrar al-Sham and other Islamist factions, who accuse the Kurds of cooperating with the regime.

Separate from Riyadh, the Syrian Democratic Forces held for the second day their own conference on Wednesday in the northern province of Hassaka.

The Syrian Kurds' exclusion from the talks in Riyadh is widely seen as a concession to Turkey, which with its large Kurdish population has been concerned about Kurdish autonomy in Syria and the YPG's ties to the Kurdistan Workers' Party (PKK).

cw/jil (AFP, AP, dpa, Reuters)