UN Secretary General Ban Ki-moon said Saturday he was "encouraged" by talks in Vienna bringing together the main outside players in the four-year-old Syria crisis for the first time.

"I am encouraged that the participants have reached a mutual understanding on a number of key issues," Ban told a press briefing in Geneva after meeting the head of the International Committee of the Red Cross (ICRC), Peter Maurer.

Top diplomats from 17 countries, including Iran, as well as the United Nations and the European Union, attended the unprecedented talks on Friday, though the Syrian regime and the opposition were not represented.

They sought common ground over a conflict that has claimed a quarter of a million lives and triggered an exodus of refugees to Europe.

US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov said they had agreed that Syria must emerge from the conflict as a unified secular state.

However, he and Lavrov disagreed over whether President Bashar al-Assad should step down immediately.

The West and Gulf monarchies led by Saudi Arabia want Assad to step down, but Russia and Iran insist he has a right to play a role in an eventual transition towards a mooted unity government and later elections.

Another round of talks will be held in two weeks.

Also Saturday, Ban and the ICRC's Maurer issued a joint statement appealing for urgent action to address growing instability and human suffering around the world and to enforce international humanitarian law.

"Rarely before have we witnessed so many people on the move, so much instability, so much suffering," Maurer said.

The statement said conflicts and violence had forced 60 million people from their homes -- the highest figure since World War II.

Ban said in the statement: "In the face of blatant inhumanity, the world has responded with disturbing paralysis... The world must reaffirm its humanity and uphold its commitments under international humanitarian law."