Syria peace talks: UN envoy says 'concrete changes' needed
UN special envoy Staffan de Mistura has said that "concrete" changes on the ground are needed in Syria in order for the peace talks in Geneva to succeed.
Mr de Mistura met government officials on Tuesday on the second day of meetings aimed at ending the conflict.
But talks with the opposition were called off amid complaints of major attacks against rebel forces.
The opposition says it will not negotiate unless the government ends its sieges and air strikes on rebels.
More than 250,000 people have died in almost five years of war in Syria.
Mr de Mistura said the talks were an "uphill" challenge as trust between both sides was "close to zero".
"The test of whether these talks are going to be serious will be... if something changes on the ground while we are doing talks," he told the BBC in an interview in Geneva.
"We need something concrete. Otherwise, we, the UN, will be the first one to say 'thank you, but we are looking for something concrete here'."
'No talks about talks'
The High Negotiation Committee (HNC), the opposition umbrella group, has warned that it will not engage in negotiations unless sieges and air strikes on rebel-held areas end, but the government has so far not agreed.
The head of the government delegation, Bashar al-Jaafari, has said the opposition is "not serious" about peace and that there should be no preconditions for talks.
The opposition has claimed that Syrian forces, backed by Russian air strikes, have intensified their campaign against rebel positions in the west of the country.
The offensive was reportedly threatening rebel supply lines into the northern city of Aleppo.
Diplomats have admitted, off the record, that the talks in Geneva could collapse at any moment.
However, Mr de Mistura said that there was a "sense of urgency" among the participants, as "they know this conflict has gone too long".
"We are not here to have another Geneva talks. We are not here to have talks about talks," he said.
Eleven million people have fled their homes as forces loyal to President Bashar al-Assad and those opposed to his rule battle each other, as well as jihadist militants from so-called Islamic State (IS).