The opposition wants to start talks by focusing on this issue while the government wants to address it near the end of talks, demanding that putting an end to "terrorism" is still its first priority.
Still, opposition spokesman Louay Safi said the fifth day of talks marked a "positive step forward."
Rebels fighting Syrian President Bashar al-Assad insist he must leave power, while the Syrian government has said Mr. Assad's role is not up for debate at the peace conference.
Also Wednesday, Turkish security forces attacked a convoy of al-Qaida-linked rebel vehicles in Syria in retaliation for cross-border fire on Tuesday.
Troops opened fire on Islamic State of Iraq and the Levant positions in northern Syria after a mortar shell fired from Syria landed in Turkish territory during clashes between ISIL and the Free Syrian Army.
Syria's conflict began in March 2011 as peaceful protests against the government before spiraling into a civil war that the U.N. says has killed well over 100,000 people and forced nearly 9 million from their homes.