Russia and Iran have agreed a schedule for finishing building the Bushehr nuclear plant, reports from Russia say.
Iran insists its nuclear programme is purely for civilian purposes
"Difficulties with the Iranian client are resolved and we have agreement on the timetable for construction," said the state contractor, Atomstroieksport.
The company's president said details would be released later this month.
Work by engineers on the plant has been dogged by delays. Russia says Iran is behind on payments, but Iran says work has been stalled for political reasons.
The US and its European allies on the UN Security Council have been pushing for tougher UN sanctions because of Tehran's refusal to end uranium enrichment.
However, correspondents say last week's US National Intelligence Estimate on Iran, which said the country had halted its nuclear weapons programme in 2003, has raised questions about the need for new measures.
Iran's nuclear programme began in 1974 with plans to build a nuclear power station near the south-western port of Bushehr with German assistance.
The project was abandoned because of the Islamic revolution five years later, but revived in 1992 when Tehran signed an agreement with Russia to resume work at the site.
There are two pressurised water reactors at the site, one of which is reportedly near completion and likely to be the first major Iranian reactor to go on stream.
Speaking shortly before the Russian and Iranian foreign ministers were scheduled to meet in Moscow, Atomstroieksport president Sergei Shmatko announced that the two countries had agreed to complete building the $1bn (£490m) plant at Bushehr.
"Difficulties with the Iranian client are resolved and we have agreement on the timetable for construction. I shall call it more precisely at the end of December," he said.
Mr Shmatko said the controversial delivery of nuclear fuel, after which the plant could begin operating within six months, would go ahead, although he again did not say when.
"We absolutely, definitely intend to build the Bushehr atomic power station and intend definitely to deliver the fuel to the plant," he stressed.
He also raised the prospect of a joint Russian-Iranian venture to "ensure security" at the plant, the RIA-Novosti agency reported.