GENEVA: UN Syria envoy Staffan de Mistura said on Saturday he expected "hiccups" in a cessation of hostilities that came into force at midnight Damascus time (2200 GMT) on Friday, and urged restraint in curbing any new outbreaks of fighting.

"There is a high chance we should expect such hiccups" in the pause in fighting brokered by the United States and Russia, he told reporters in Geneva after briefing the United Nations Security Council in New York via videolink.

"The important point is whether those incidents will be brought quickly under control and contained. That is going to be the test."

Incidents in Damascus and Deraa were reported within the first few minutes of the cessation of hostilities, but those towns quickly calmed down, he said.

His office was investigating a report of another breach, De Mistura said without elaborating, and countries backing the Syrian peace process would meet on Saturday in Geneva to assess the state of the cessation of hostilities.

"Let's pray that this works because frankly, this is the best opportunity we can imagine the Syrian people will have and have had for the last five years in order to see something better and hopefully something related to peace. Facts will tell," he said.

The cessation of hostilities will be monitored by the United States and Russia via centres in Washington, Moscow, Amman and the Syrian city of Latakia, and at the UN in Geneva.

In case fighting breaks out, the United States and Russia will alert the other countries backing the peace process. A military response should be a last resort and proportionate, he said.

If the cessation of hostilities holds, De Mistura plans to start a second round of peace talks between the warring parties on March 7, running for three weeks in the first phase.

The agenda would remain the same as in the first round, which De Mistura abruptly suspended on Feb. 3: a new inclusive government, a new constitution and new parliamentary and presidential elections within 18 months.

He declined to say if Kurdish representatives, who were excluded from the first round, would be invited to take part.