"Our general impression is that there is a very good chance that must not be missed," Lavrov said on Saturday.
"Now there are no fundamental disagreements on the practical questions that need to be resolved," he said.
All that is necessary now is to "correctly draw up the agreement we have reached in diplomatic language," he said.
Lavrov warned against adding further conditions for Iran when nuclear talks resume in Geneva on Wednesday.
He said the talks should not focus on "submitting some artificial additions that do not help solve the main task and don't essentially change anything."
On Thursday, Lavrov said amendments made by a member of the Sextet to a draft proposal during the recent Iran nuclear talks in Geneva spoiled efforts to clinch a deal.
Lavrov added that Iran and the six powers were close to reaching an agreement during the negotiations, but last-minute amendments to the draft document blocked a deal. Analysts say France was the reason behind the failure of the talks to yield an agreement.
The so-called P5+1 group negotiating with Tehran is made up of the five permanent members of the UN Security Council -- Britain, China, France, Russia and the United States -- plus Germany.
RA/SHI