Turkey's state-run Anadolu Agency said on Wednesday, Censor.NET reports citing Reuters.
The states will aim to put it into effect by midnight.
Anadolu, citing sources, said the two countries have reached a consensus that will be presented to participants in the conflict on expanding the cease-fire that was established in Aleppo earlier this month.
A spokesman at Turkey's foreign ministry said he had no immediate comment on the report.
Russia, Iran and Turkey said last week they were ready to help broker a peace deal after holding talks in Moscow where they adopted a declaration setting out the principles any agreement should adhere to.
Arrangements for the talks, which would not include the United States and be distinct from separate intermittent U.N.-brokered negotiations, remain hazy, but Moscow has said they would take place in Kazakhstan, a close ally.
Russia's foreign minister on Tuesday said the Syrian government was consulting with the opposition ahead of possible peace talks, while a Saudi-backed opposition group said it knew nothing of the negotiations but supported a ceasefire.
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