The move, welcomed by the United Nations, has been met with scepticism from the United States as the so-called safe-zones will closed for warplanes of the United States and those of the U.S.-led coalition.

As Bloomberg reports, the three countries signed a memorandum on the creation of so-called de-escalation areas on Thursday after two days of talks in Kazakhstan that also included representatives of the Syrian government and rebel groups.

Opposition leaders distanced themselves from the plan, saying they can't accept Iran as a guarantor of the truce and that they want "clear and tangible" guarantees the deal will be enforced.