The launch of the Bushehr plant's nuclear reactor has frequently been delayed. Russian and Iranian officials have given different dates for the start-up. Iran's foreign minister said last year the plant would launch in mid-2008.
Russia has already delivered nuclear fuel under a $1 billion contract to build the Bushehr plant on the Gulf coast in southwest Iran. Russia has blamed previous delays on problems with receiving payment from Iran.
"Work is ongoing and certain difficulties which arose, including those connected with timely financing, are being resolved due to joint efforts between the Iranian purchaser and the Russian contractor," Tass quoted Sergei Kiriyenko, the head of Russia's Rosatom nuclear corporation, as saying.
"Next year we should conclude all the work," Kiriyenko was quoted as saying. Kiriyenko was in Caracas, Venezuela, accompanying President Dmitry Medvedev on a visit.
Russia agreed in 1995 to build the plant on the site of an earlier project begun in the 1970s by German firm Siemens. The Siemens project was disrupted by Iran's 1979 Islamic revolution and the 1980-88 Iran-Iraq war.
"The position of Russia has not changed: that Bushehr should be finished as soon as possible," a spokesman for Rosatom said. "But that must not affect the security of the plant and the functioning of its systems."
"The main question is the integration of Russian equipment with the equipment delivered to the plant at Bushehr by the Germans," the spokesman said.
Atomstroyexport, the Russian firm building the plant, said in September the plant was nearing completion and that it would start "technological work" in December 2008 to February 2009 that would put the plant on an "irreversible final" course.
Analysts say Russia has used Bushehr as a lever in relations with Tehran, which is at loggerheads with the West over its nuclear programme.
Russia's Foreign Minister Sergei Lavrov has repeatedly said Moscow does not want Iran to be armed with nuclear weapons but that Russia has seen no evidence that Tehran is seeking to build atomic bombs.
Iran denies having a bomb programme and says it has the right to develop civilian nuclear power.
Russian and U.S. officials point to cooperation over Iran as an area where Moscow and Washington have been able to work together despite a general cooling of ties.
