* U.N. atomic agency seeks access to sites and officials in Iran
* West accuses Tehran of stonewalling inquiry, Parchin clean-up
* IAEA chief says Parchin access would still be "useful"
* Iran rejects allegations of nuclear weapon research
By Fredrik Dahl
VIENNA, Dec 10 (Reuters) - U.N. nuclear inspectors will press Iran this week for a long-sought green light to visit a key military site, although suspected clean-up work may make it difficult to find evidence of any illicit atomic bomb research there.
Thursday's talks in Tehran could provide clues as to whether the Islamic state may now be more willing to start addressing growing international concerns over its disputed atomic activity following U.S. President Barack Obama's re-election last month.
The stakes are high: Israel - widely believed to be the Middle East's only nuclear-armed power - has threatened military action if diplomacy fails to prevent its arch-foe from acquiring doomsday weaponry. Iran says it would hit back hard if attacked.
But Western diplomats are not optimistic about the chances of a breakthrough in the new discussions in the Iranian capital, after a series of meetings between Iran and the International Atomic Energy Agency (IAEA) this year failed to make headway.
The Vienna-based U.N. nuclear watchdog wants Iran to allow its inspectors to visit sites, interview officials and study documents as part of an IAEA investigation - largely stymied by Iranian stonewalling for four years - into possible military dimensions to the country's nuclear programme.
Iran, which rejects accusations of a covert bid to develop the means and technologies needed to develop nuclear arms, says it must first reach a framework agreement with the IAEA on how the inquiry should be done before providing any such access.
"I have no sense that Iran wants an agreement. Iran wants the issue to go away," one Western envoy in the Austrian capital said, predicting "another nothing meeting".
The IAEA's talks with Iran are separate from - but still closely linked to - efforts by six world powers to resolve the decade-long nuclear dispute with Iran before it degenerates into a new war that could send economic shock waves around the world.
Diplomacy between Iran, a major oil exporter, and the United States, China, Russia, France, Germany, and Britain has been deadlocked since a June meeting that ended without success.
Both sides now say they want to resume talks soon - after Obama's re-election which some analysts say may give fresh impetus to the search for a negotiated settlement - and diplomats expect a new meeting early next year.
PARCHIN VISIT WOULD STILL BE "USEFUL"
Iran has faced a tightening of Western trade sanctions which the United States and its allies hope will force the Islamic Republic to curb its uranium enrichment programme.
Tehran says its aims are entirely peaceful but is showing no sign of backing down, instead signalling continued defiance by rapidly expanding its capacity to refine uranium, which can fuel nuclear power plants but also provide material for bombs.
The powers also want Iran to cooperate with the IAEA to clear up suspicions of past, and possibly still ongoing, activities relevant for the development of nuclear bombs.
The IAEA's priority is to examine the sprawling Parchin military complex southeast of Tehran, where it believes Iran has carried out explosives tests with nuclear applications.
IAEA chief Yukiya Amano last week said the agency still wanted to go to Parchin, despite what Western officials say are apparent Iranian efforts to "sanitise" the site, including demolition of buildings, tearing down of fences and a removal of soil that has been replaced with new dirt.
"I cannot guarantee that we can find something or not. But I continue to believe that having access is very useful to have a better understanding of past and current activities at Parchin," Amano said in Washington, according to a transcript.
Tehran says Parchin is a conventional military facility and has dismissed Western allegations that it is trying to eliminate evidence of any illicit nuclear-related experiments.
The Institute for Science and International Security (ISIS), a U.S.-based think-tank, last month said satellite imagery suggested that two buildings at Parchin may have new roofs, or possibly that the old ones had been repainted.
ISIS said continued construction activity there would degrade "the chance of obtaining reliable environmental samples if and when IAEA inspectors gain access to the site."
Asked how the West would react if Iran suddenly were to let inspectors go to Parchin, the Western diplomat said: "You are not going to see us welcoming the move and say this is great. We would say it is long past due and see what the IAEA can learn." (Editing by Mark Heinrich)