Speaking at a Syria donors' conference in London, Zarif insisted Tehran believed that intra-Syrian talks were the "only way out" of the bloody civil war tearing the country apart.
Zarif's was the first visit to Britain by an Iranian foreign minister to Britain in 16 years.
International donors were meeting on the Syria crisis just hours after the peace talks in Geneva were suspended Wednesday until February 25.
The "brutal images of barbarism" produced by the conflict "continue to agonise the entire humanity", he said.
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"We have also underlined that outside actors should facilitate such dialogue and not seek to dictate its parameters or outcome."
"We hope that the pause in the Geneva talks is only temporary," he added.
Zarif said Iran had provided USD 2.8 billion in aid so far, targeted at internally displaced people.
"However, considering the extent of the humanitarian catastrophe, much more needs to be done inside as well as outside Syria," he said.
He reiterated Iran's "readiness to engage in all efforts to bring an immediate ceasefire and to collaborate in humanitarian endeavours to alleviate the suffering of the Syrian people".