The United States and Russia must make Syria’s cessation of hostilities work or else it may become essential to suspend the resumption of peace talks, U.N. Syria envoy Staffan de Mistura said in an interview with Reuters on Tuesday.

Since the cessation of hostilities agreement brokered by Russia and the U.S. to end the nearly 5 years of bloodshed came into force on Saturday, the Syrian government and the opposition have exchanged accusations of violating the deal, yet international observers have reported a decline in violence.

With no breakthrough on the horizon regarding the cessation of hostilities and access for humanitarian aid, de Mistura said he could “slightly” postpone the next round of peace talks, which has been scheduled for Monday, March 7.

“The decision on whether they will be on Monday or slightly later will be taken in the next few days, depending on what is happening on the ground,” he said.

“We don’t want discussions in Geneva to become a discussion about infringements or not of the ceasefire, we want them to actually address the core of everything.”

The United Nations hopes that the truce will allow humanitarian aid to be delivered into besieged areas and provide an opportunity to revive the peace talks, which collapsed before they even started a month ago.

“So we will be in the next few days analyzing how far both the ceasefire and the humanitarian access have come, so that they don’t become hostages of the talks and the talks don’t become hostages to progress on that,” de Mistura said.

Both, the United States and Russia, who have drawn up the cessation of hostilities agreement, are required to share information and monitor the truce because the United Nations is not involved in that, de Mistura told reporters in an interview at the United Nations in Geneva.

Thus, the two countries need to share common maps of the battlefield and monitor the situation with drones and satellites, as deploy thousands of observers on the ground is practically impossible. The United Nations only had general maps of the situation before the ceasefire, he said.

De Mistura said he expected to see attempts to disrupt the ceasefire, and these needed to be contained to avoid them spreading and undermining the credibility of the truce.