VIENNA, Austria (AP) – Moscow has warned Iran that 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 Tuesday.

Separately, an American official told The Associated Press that the Russians are 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 U.N. Security Council demands. Both men demanded anonymity in exchange for speaking to the AP because their information was confidential.

The increased Russian pressure comes at a time Iran already appears to be ready to compromise on a key international request – that it lift its shroud of secrecy over 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 later to U.N. to 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.

With a third set of sanctions looming, Iran last month told the International Atomic Energy Agency – the U.N. nuclear watchdog that is investigating Iran – that if would answer questions outstanding for years about past experiments and activities that could be linked to a weapons program. That – 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 American-led moves to implement new and harsher sanctions.

Last month, IAEA inspectors visited the reactor, near the city of Arak. And a second European diplomat told the AP that the Iran had recently began providing valuable information on “four of 10 questions” that the agency wanted answered.

IAEA officials declined 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 Tehran posses diagrams showing 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.

It and China have blocked attempts by America, Britain and France – the three other permanent Security Council members – to impose harsh U.N. sanctions and have hobbled efforts to move forward on new penalties this summer in the face of continued Iranian refusal to freeze its enrichment activities.

With Iran showing signs of that it is ready to shed light on some of its past unexplained activities, the American-led push for new, more rigorous sanctions has turned into a “steep climb that has become steeper,” the American official said.

Still, it has used Bushehr, built by Russian technicians, as a lever. The first European diplomat said Tuesday that Russian officials told the Iranians about two weeks ago that Russian fuel roads to the Bushehr reactor would be held back as long as unresolved questions about Tehran’s past nuclear activities remained.

That followed a Russian warning in March that the rods would be withheld as long as the Islamic republic ignored demands that it freeze uranium enrichment.

In Algeria, Iranian President Ahmadinejad said Tuesday that his country will continue pursuing nuclear energy and will refuse to talk with any countries that do not recognize Tehran’s right to civilian nuclear power.

“Iran cannot hold discussions with countries that do not recognize this right,” he told a news conference. “The Iranian people will … continue their efforts toward acquiring nuclear energy for peaceful ends.”

Mr. Ahmadinejad denounced countries that have “mobilized all their energy to isolate” Iran over its nuclear program. He did not identify any countries.

His visit to Algeria has put the North African country in an awkward diplomatic position, since the Algerian government is an ally in the American-led war on terrorism and signed a deal on nuclear energy cooperation with Washington in June.