Hassan commented on the ongoing clashes in Aleppo, which have escalated in recent days despite a truce between the government and the opposition groups.

Hassan said the situation on the ground was very difficult, and the impact on the civilian population was unbearable with multiple fightings as well as numerous factions fighting each other.

Fighting around Aleppo has become the biggest threat to the fragile cessation of hostilities that went into force on Feb. 27. It has also contributed to the decision by the main opposition delegation to suspend its formal participation in peace talks.

There was no progress in the Geneva negotiations, Hassan added. He believed this was in reaction to talks between the United States and Russia on the nature of political transition. The negotiations were entering a sensitive phase and this impacted the calculations of the warring parties, argued Hassan.

Another issue that Hassan underscored in the BBC interview was that there was no flexibility on the government's side to grant humanitarian access to beseiged areas. News reports say that more than 40,000 Syrians have fled fighting in that area.

Complicating the situation, he added, was the opposition and the international coalition did not recognize the results of the recently-held parliamentary election. Syria's ruling Baath party and its allies won a majority of seats in parliamentary elections on April 13 across government-held parts of the country.

Video forthcoming.