Speaking in Canberra after meeting with his Australian counterpart Julie Bishop, Zarif underlined Iran's stance on the need for a ceasefire and a political solution in Syria.
"The fact that a semi-ceasefire has been holding in Syria is welcome news, it's something that we've been asking for at least two-and-a-half, three years," he said.
"The fact that Russia announced that it's withdrawing part of its forces indicates that they don't see an imminent need for resort to force in maintaining the ceasefire.
"That in and of itself should be a positive sign. Now we have to wait and see."
Zarif said while the ceasefire did not include Daesh, the so-called Islamic State group, and the Al-Qaeda linked extremist group Al-Nusra Front or their collaborators, the international community was united against them.
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"The message that the international community has been sending to Daesh, and should be sending to Daesh and other extremist organisations, is that our fight against them is relentless," Zarif said.
"We will not stop and I believe the entire international community is united in that."
Zarif said he did not think anybody should consider Daesh or other extremist organisations as a leverage "even for temporary political gains".
"And I hope that message can be driven home everywhere in the region, particularly as we see more and more instances of carnage in terrorism in our region carried out by Daesh," he said.
President Vladimir Putin called long-standing ally Bashar al-Assad on Monday to inform him that Moscow will withdraw the bulk of its forces from Syria, a move hailed by the United Nations Security Council as a "positive step" for the fraught peace negotiations.
But hopes for a breakthrough at the Geneva talks remain remote with both sides locked in a bitter dispute over the future of the Syrian president.