Syria's ambassador to Iraq has defected to the opposition and urged other senior Syrian politicians and members of the military to do the same.

In an exclusive interview to Al-Jazeera, Nawaf al-Fares said that his decision came in the wake of what he described as horrible massacre committed against the Syrian people by the regime.

Fares is the first senior Syrian diplomat to abandon the government of President Bashar al-Assad.

The move comes just a week after a Syrian general from a powerful family close to President Assad also defected.

In the meantime, Western nations are urging the UN to threaten tough sanctions against Syria.

They want the threat to be part of a Security Council resolution on the future of the UN's observer mission in the country.

A new resolution must be passed before the mission's mandate ends on Friday next week.