The long-negotiated truce has been holding for two days, but the United Nations says it has still not been able to deliver humanitarian aid.
Activist groups monitoring the situation in Syria say there have been no civilian deaths recorded since the ceasefire came into effect on Monday.
The deal, struck by International Syria Support Group co-chairs United States and Russia, is to be renewed every 48 hours.
The decision to renew is based on whether US Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov can reach a consensus.
US State Department spokesman, Mark Toner, said the pair agreed to extend the truce over the phone.
"I think there was agreement between the two of them that as a whole, despite sporadic reports of violence, as a whole, the arrangement is holding, and violence is, I'd say, significantly lower in comparison to previous days and weeks. And I can also just add that as part of the conversation, they agreed to discuss and agree and extend the cessation for another 48 hours."
If the ceasefire holds for a week, the US and Russia will coordinate military airstrikes on militant groups - namely the self-proclaimed Islamic State and Jabhat Fateh al-Sham.
But the predominant international focus at the moment is sending much-needed aid to besieged areas.
Some trucks have crossed into Syria from Turkey, with one delivering food and children's toys to the border city of Jarablus.
But the United Nations says its trucks, scheduled to deliver supplies to the devastated city of Aleppo, have been unable to enter Syria.
UN Secretary General Ban-Ki Moon says disagreements between warring sides and safety concerns are causing the delays.
"All these 20 truckloads are ready and they were supposed to deliver them today. But unfortunately because of all this arrangement for making sure the security and safety of the people, humanitarian workers including drivers, have not been made yet. So they are now at the border."
Syrian government forces and rebel militias are reportedly preparing to withdraw from a key road into Aleppo.
But Syria's foreign ministry says it won't allow any aid to enter the rebel-held side of Aleppo without coordination between the Assad government and the UN.
Ban Ki-Moon is turning to Russia to persuade Syria to let the trucks through.
"So it is crucially important that the necessary arrangements, security arrangements, should be given so that they can be allowed to cross the lines. I have been urging the Russian government to make sure that they exercise influence on Syrian government and also the American side to make sure that the Syrian armed groups also fully cooperate. We are working very hard. We are very much committed."
While the ceasefire is largely holding, incidents of shelling by various rebel forces and air strikes by pro-government forces have been reported.
The Russian military claims rebels have violated the ceasefire 60 times since its start.
Spokesman Lieutenant General Viktor Poznikhir says Russia is fully adhering to the deal.
"We also note that some armed groups controlled by the USA, such as Ahrar al-Sham, have openly stated their unwillingness to cease fire. The greatest number of violations is associated precisely with these groups. However, taking into account the importance of unconditional implementation of the agreements reached, the Russian side is in favour of extending the regime of cessation of combat activities in the whole territory of Syria for another 48 hours. Russia is fully implementating the obligations which it has undertaken."
The desire for the ceasefire to be successful is being felt by not only Syrian locals, but the greater international community.
Aside from the US and Russia, leaders from various European countries, and Australia, have expressed their hope the truce holds.
British Prime Minister Theresa May has told her parliament Syria's future has become intrinsically linked with the rest of world's.
"The agreement that has been reached between Russia and the United States about Syria is an important agreement and I think everybody in this House will want to see that working, being put into practice and actually working on the ground. I would say there have been a number of occasions where we've seen what appear to be steps forward and sadly it hasn't been possible to implement them, but I hope that this will be different this time."
Aleppo residents say they are just happy to see the skies clear for two days in a row, during the religious holiday of Eid al-Adha.
"Thank God the situation is so good. We are able to work, and God is watching over us. And thank God, this Eid is so much better than last year. Last Eid had a fair bit of destruction. Thank God, the situation is calm now and with the truce, things will be much better."
