NATO on Sunday guarded against "unrealistic expectations" for peace and democracy in the Middle East and North Africa as violence flared in Syria and Egypt.

"The whole region is going through a complicated, difficult process of reform," James Appathurai, NATO deputy assistant secretary general for political affairs and security policy, told a defense summit in Canada.

"I think it's important for the public not to have unrealistic expectations about how quickly this will happen or that the outcome is necessarily foreseen to be the one we might wish it to be," he told reporters.

"So, we have to be patient, offer support where we can, we can't impose it, and that's what we're doing."

Some 300 generals, defense ministers and officials from around the world gathered at the Halifax International Security Forum in easternmost Canada.

Although they grappled with the notion that the NATO mission in Libya had created a new paradigm for the global community to intervene in hotspots, Appathurai reaffirmed that action in Syria was not on the table.

"There is no discussion of a NATO role with regard to Syria," he said. "Responsibility to protect doesn't automatically translate into a NATO operation."

The North Atlantic Treaty Organization-led bombing campaign in Libya, launched under UN mandate, ended on October 31 after the toppling of Moamer Kadhafi's regime and his death last month.

On Sunday, Syria shrugged off looming Arab League sanctions and growing international pressure to end a lethal crackdown on protesters that has resulted in more than 3,500 deaths since mid-March, according to UN figures.

Deadly clashes broke out for the second day running in Cairo's Tahrir Square on Sunday as Egyptian riot police dueled with demonstrators angry at the slow pace of chance since Hosni Mubarak's downfall in February.

Friday had seen tens of thousands of people pack Tahrir for a rally to demand that the army transfer power to civilian rule.

The military says it will hand over power after a presidential election, which has yet to be scheduled.