Staffan de Mistura said on Tuesday that the ongoing refugee crisis facing Europe and the battle against the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) also add some "sense of urgency" for government and rebel negotiators to support the peace process.
"I do feel that there is a difference" in this talks, he said when asked why he thinks the negotiations in Geneva would succeed.
READ MORE: Moscow and Washington are not that far apart on Syria
He said the engagement of several countries, including the US and Russia, and the "unified Security Council" also led him to believe that while there will be "rocky times" ahead, the talks will "produce a momentum".
Still, de Mistura said there are several major issues that could pose roadblocks to the process, including the release of opposition detainees in Syrian prisons, and the delivery of humanitarian help to residents of Daraya outside of Damascus.
At the beginning of the meeting, negotiators observed a minute of silence for the victims of the war, which marked its fifth year anniversary on Tuesday.

'Constructive' session

Bassma Kodmani, opposition negotiator and member of the High Negotiations Committee, also called the day's session as "constructive".
"There was some joy and pride for what people believe as the beginning of the freedom of the Syrian people," Kodmani said.
But she also acknowledged that there are still no result on the issue of release of detainees, which she said "is not up for negotiation".
She said "daily executions" of at least 50 detainees continue in different prisons in Syria.
Examining the proxy war in Syria
As talks enter its second day in the Swiss city of Geneva, a Syrian opposition monitoring group is reporting intense air strikes in and around the historic town of Palmyra amid fighting between pro-government forces and ISIL.
The Britain-based Syrian Observatory for Human Rights says there were casualties on both sides in Tuesday's battles, without providing a precise figure.
Al Manar TV, run by Lebanon's Hezbollah group, says Syrian troops and their allies captured "Hill 900," which is the highest in the area and overlooks Palmyra.
Hezbollah is fighting alongside forces loyal to Syrian President Bashar al-Assad.
Palmyra, home to famed Roman ruins, has been under the firm control of ISIL since the armed group captured it in May last year.
ISIL and the al-Qaeda's branch in Syria, known as the Nusra Front, are not part of a cease-fire that was brokered by Russia and the US and went into effect on February 27.
The Syrian conflict has killed more than 250,000 people and displaced almost half the country's prewar population of 23 million since it began in March 2011.
The war has also led to a wave of refugees in Europe.
Source: Al Jazeera and agencies
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