Syria's President Bashar al-Assad has vowed to retake the entire country but warned it could take a "long time," in an exclusive interview with AFP as international pressure grows for a ceasefire, the news agency reports.

Speaking at his office in Damascus, hours before a new ceasefire plan was announced early Friday, February 12 by world powers in Munich, Assad said he backed peace talks but that negotiations do "not mean that we stop fighting terrorism."

Regime forces backed by Russian air strikes have registered major advances in recent days, particularly in northern Aleppo province, where Assad said the army was seeking to sever the opposition's supply route from Turkey.

He also addressed the massive flow of refugees from his country, saying it was up to Europe to stop "giving cover to terrorists" so Syrians could return home. Dressed in a dark blue suit, Assad appeared bolstered by his recent military gains, and said his eventual goal was to retake all of Syria.

"Regardless of whether we can do that or not, this is a goal we are seeking to achieve without any hesitation," he said. "It makes no sense for us to say that we will give up any part."

Assad said it would be possible to "put an end to this problem in less than a year" if opposition supply routes from Turkey, Jordan and Iraq were cut.

But if not, he said, "the solution will take a long time and will incur a heavy price."

"The main battle is about cutting the road between Aleppo and Turkey, for Turkey is the main conduit of supplies for the terrorists," Assad said.

"I would like to ask every person who left Syria to come back," he said.

"They would ask 'why should I come back? Has terrorism stopped?'"

Instead, he urged Europe's governments "which have been a direct cause for the emigration of these people, by giving cover to terrorists in the beginning and through sanctions imposed on Syria, to help in making the Syrians return to their country".