"A further dragging out of these questions will further worsen the existing delays to the timetable for building the [power station]," the official added.
The United States has been pressuring Russia to stop work on the Bushehr plant in southwest Iran because it suspects Tehran is planning to start a nuclear weapons programme. Nuclear arms denial
Moscow has argued that Tehran does not have the capability to make nuclear weapons while Iran says it has a right to develop its civilian nuclear sector and denies seeking nuclear arms.
"It is stubbornness and pride on Iran's part that has led to this impasse, and it can only lead to disaster for Iran"
Diom1982, Cork, Ireland
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Russia is scheduled to deliver fuel to the plant this month, with the station's reactor starting work in September.
Iranian negotiators have been holding talks with Atomstroiexport, the Russian state-owned firm building the plant, and offered more money to overcome delays, Mohammad Saeedi, deputy head of Iran's nuclear energy organisation, told Reuters on Friday.
"Of course there are some delays but the Russian company and the Iranian side have prepared a schedule which will decrease and compensate for this delay," Saeedi, who headed an Iranian delegation at talks in Moscow, said.
"Atomstroiexport has financial problems and has asked Iran to pay part of the contract money before what was said in the contract." Nuclear timetable
He said a Russian delegation would travel to Tehran next week to discuss the timetable for starting up the plant.
"Iran believes that there is no obstacle to deliver fuel to Iran and based on the agreement it is necessary that the Russian side delivers the fuel to Iran in March and that the power plant starts operations in September," he said.
In New York, diplomats from the United Nations security council and Germany were discussing possible new sanctions against Iran, which would tighten measures adopted in December.
The fresh sanctions could include a travel ban on officials involved in illicit nuclear work, barring Iran from exporting arms, financial sanctions and possible restrictions on export credits to Iran, diplomats said.
The December sanctions were adopted by the 15-member Security Council after Tehran refused to halt a uranium enrichment programme that could produce fuel for nuclear power stations but also material to make atomic bombs.