The truce between Syrian President Bashar Assad's government and armed opposition groups, brokered by Russia and the United States, has defied expectations and led to the first significant decline in violence in Syria's nearly five-year civil war.
The United Nations is hoping it can now restart talks on a political transition that collapsed last month in Geneva.
The opposition, represented by the Riyadh-based High Negotiations Committee, had held off on committing to the talks but Monday said the 10-day-old "cessation of hostilities" was making a difference.
"After consultations, the High Negotiations Committee agreed to go to Geneva. The delegation is expected to arrive on Friday," Riad Naasan Agha, a spokesman for the group, told AFP.
"We have noticed a sharp decline in ceasefire violations in recent days and progress in the humanitarian file," particularly with regards to aid deliveries to besieged towns, Agha said.
The ceasefire agreed on Feb. 27 is part of the biggest diplomatic effort yet to resolve Syria's conflict, which has killed more than 270,000 and forced millions of people from their homes.
Russia and the United States are on opposing sides of the conflict -- Moscow backs Assad and Washington supports the opposition -- but the two powers have made a concerted push for the ceasefire and further peace efforts to succeed.
Observers say the partial truce, which does not apply to extremists from the Daesh group or the Al-Qaeda-affiliated Al-Nusra Front, has largely held despite widespread scepticism before it took effect.
Moscow, which has provided a daily account of ceasefire violations, said Monday that the truce was still "in general" holding apart from unspecified "isolated provocations and shelling".
It said Russian planes were continuing to carry out airstrikes against Daesh (ISIL) and Al-Nusra in three provinces, including on the main Daesh stronghold of Raqa.
A US-led coalition has also been carrying out airstrikes since September 2014 against Daesh in both Syria and Iraq, where the extremist group has seized control of significant territory.
The UN Syria envoy, Staffan de Mistura, said at the weekend that the Geneva peace talks would resume Thursday, but many delegates are not expected to arrive until several days later.
A plan agreed by world powers last year calls for a ceasefire, the creation of a transitional body, the drafting of a new constitution and fresh elections.