The rubbles after airstrikes in Ghouta on the outskirts of Damascus on April 4 (Photo: AFP/ VNA)

The State Department said Washington hopes the plan will help stem the violence, but expressed concern about Iran's involvement in the deal. Russia and Iran joined with Turkey to sign a safe zone pact earlier in the week.

Turkish President Recep Tayyip  Erdogan said the safe zones, which include Idlib province, part of Aleppo province, the El-Rastan region in Homs, and parts of Damascus and Daraa, will solve 50 percent of the Syrian issue. Erdogan described the plan as a “new concept”, distinct from Turkey’s previous proposals for terror-free safe zones.