Moscow has warned Tehran it will not deliver fuel to a nearly completed Russian-built nuclear reactor unless Tehran lifts the veil of secrecy on suspicious past atomic activities, a European diplomat said.
Separately, a US official said Russia was not meeting other commitments that would allow the Iranians to activate the Bushehr nuclear reactor and suggested the delays were an attempt to pressure Tehran into showing more compliance with UN Security Council demands.
The increased Russian pressure came at a time when Iran appeared to be ready to compromise on a key international request -- that it fully explain past activities that heightened suspicions it might be looking to develop a nuclear arms program.
Those fears led to Security Council demands that Iran suspend its uranium enrichment program -- and to UN sanctions over Tehran's refusal to mothball the program, which can be used both to generate power and to make the fissile core of nuclear warheads.
In Algeria, Iranian President Mahmoud Ahmadinejad said on Tuesday that his country would continue pursuing nuclear energy and will refuse to talk with any countries that do not recognize Tehran's right to civilian nuclear power.
But Tehran last month told the International Atomic Energy Agency (IAEA) that it would answer questions about past experiments and activities that could be linked to a weapons program. That -- as well as a slowdown in enrichment activities and a decision to lift a ban on IAEA inspections of a reactor that will produce plutonium once it is completed -- appeared aimed at deflecting US-led moves to implement a third set of sanctions.
Last month, IAEA inspectors visited the reactor, near the city of Arak. And a second European diplomat said that the Iran had recently began providing valuable information on "four of 10 questions" that the agency wanted answered.
IAEA officials declined to comment.
But concerns detailed by past IAEA reports have included suspicions that Tehran has secretly developed elements of a more sophisticated enrichment program than the one it has made public; that it might not have accounted for all the plutonium it processed in past experiments and that its military might have been involved in enrichment, a program that Tehran insists is strictly civilian run.
Revelations that Iran has diagrams of how to form uranium metal into the shape of warheads have heightened concerns.
Russia has played a complicated role in attempts to pressure Tehran to comply with international demands.