The unification of opposition forces, which began at the end of last month in Aleppo, comes as regime forces continue to bombard opposition-held areas.
In Geneva, UN Special Envoy Staffan de Mistura has continued his consultations with representatives from across Syria.
After more than three years of fighting, gains made in the latest offensive could enable opposition groups to put pressure on regime representatives in Geneva - at a time when their forces and their Hizballah allies are coming under attack in the Qalamoun region near the Lebanese border and have suffered major setbacks in Idlib and Jisr al-Shughur in the north.
"Moderate" factions including the Nur al-Din Zinki Movement, Army of the Mujahidin, Al-Fateh Brigades, Sultan Murad Brigades and the Furqan Brigades have joined the operation.
The Fursan al-Haq Brigades, the Suqur al-Jabal Brigades, Battalion 101, Battalion 13 and Battalion 16 have also joined Fateh Halab, and are known to have received US-made anti-tank missiles and training in the Gulf, giving them an edge over Syrian regime forces.
The statement also named Abu Ammara Brigades, the Army of Sunna, and Bayariq al-Islam as joining the operation.
These factions are seen as Islamist groups and do not enjoy good relations with the countries backing the Syrian opposition - although they are not designated "terrorists" by Western powers.
The Fateh Halab war room was set up in late April by the largest Syrian opposition factions in the city - the Levantine Front, Ahrar al-Sham, Faylaq al-Sham, the Levant Revolutionary Brigades, the Army of Islam, Fastaqim Kama Umirt and the Dawn of the Caliphate Brigades.
The operation now comprises all armed opposition factions in Aleppo except for the al-Qaeda-affiliated Nusra Front and the Ansar al-Din Movement, made up of the Sham al-Islam Brigades and the Jaysh Muhajirin wal Ansar. Both are designated terrorist organisations by Washington.
The exclusion of groups labelled as “terrorist” means the operation has a better chance of receiving regional and international military support. Access to advanced anti-tank missiles is likely to be highly significant, having proved decisive against Syrian armour in Idlib and Jisr al-Shughur.
Opposition forces have carried the offensive against regime-controlled locations north of the city in recent days. According to a source in the Levantine Front, a joint opposition force was able to destroy a regime command post in the Sayf al-Dawla district on May 5, killing 17 soldiers.
A tank and heavy artillery position were taken out by anti-tank missiles in Bashkoy, north of Aleppo on May 6.
Meanwhile in Geneva, talks have continued under the gaze of UN officials. A source close to the leadership of the Levantine Front, however, said opposition leaders in Aleppo were dissatisfied with the way De Mistura had handled the talks, saying many of those invited to attend lacked political weight on the ground.
This is an edited translation from our Arabic edition.