United Nations General-Secretary Ban Ki-moon said Saturday that this week's talks on the Syrian war had been taken "hostage" by the question of whether President Bashar Assad should stay or go.

"It is totally unfair and unreasonable that the fate of one person takes the whole political negotiation process hostage. It is unacceptable," Ban said in an interview with Spanish newspapers.

"The future of Assad must be decided by the Syrian people," he said.

Ban's remarks come after representatives from the US, Russia, Saudi Arabia, and more than a dozen other nations, met in Vienna for talks aimed at working towards a political transition in Syria. At the meeting, participants proposed a nationwide truce and called for the renewal of a UN-led peace process.

Ban said the UN was ready to help on both points in order to bring about "credible, inclusive and non-sectarian governance, followed by a new constitution and elections." But he also acknowledged that "substantial differences remain."

Key differences remain

One of the big points of difference is Assad's role in the transition process. Russia and Iran remain the Syrian president's main backers, while the US, its Gulf Arab allies and Turkey have called for his swift removal.

Syria's civil war has raged for more than four years, killing at least 250,000 people and forcing millions to flee their homes. The UN Office for the Coordination of Humanitarian Affairs (OCHA) says that 13.5 million people are in need of humanitarian assistance.

The conflict is complex with government forces battling opposition rebels and jihadist militant groups. The United States has been carrying out aistrikes against fighters with the self-declared "Islamic State" in Syria, but on Friday Washington announced it would also send a small contingent of special forces to the country's north to help in the anti-jihadist fight. The step would be the first deployment of US ground troops to the Middle East country.

'Enough is enough'

Also on Saturday, Ban and International Committee of the Red Cross President Peter Maurer issued what they called an "unprecedented joint warning" for states to stop conflicts, respect international law and aid refugees.

"In the face of blatant inhumanity, the world has responded with disturbing paralysis," they said in a statement. "This flouts the very raison d'etre of the United Nations."

They also called for countries to rein in armed groups and to stop the use of heavy weapons in populated areas. "Enough is enough. Even war has rules. It is time to enforce them," Ban said.

nm/jm (Reuters, AFP, AP)