* IAEA has talks in Tehran on Thursday, first since August
* U.N. nuclear inspectors "ready" to go to Parchin facility
* Western diplomats have accused Iran of removing evidence
* Islamic state rejects nuclear weapons allegations
U.N. nuclear inspectors travelling to Iran would be prepared to go to its disputed Parchin military complex if the Islamic state were to allow a visit during talks in Tehran this week, the head of their delegation said on Wednesday.
The International Atomic Energy Agency (IAEA) believes Iran has conducted explosives tests with possible nuclear applications at Parchin, a sprawling facility southeast of the Iranian capital, and has repeatedly asked for access.
Western diplomats say Iran has carried out extensive work at Parchin over the past year - including demolition of buildings and removal of soil - to cleanse it of any traces of illicit activity. But the IAEA says a visit would still be "useful".
Iran denies Western accusations of a covert bid to develop the means and technologies needed to build nuclear arms. It says Parchin is a conventional military site and has dismissed allegations of "sanitisation" there.
Thursday's talks in Tehran - the first such meeting between the IAEA and Iran since August - could indicate whether Iran is more willing to address international concerns over its nuclear programme after U.S. President Barack Obama's re-election.
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-enemy acquiring nuclear weapons. Iran says it would hit back hard if attacked.
IAEA Deputy Director General Herman Nackaerts said the aim was to reach an agreement on outstanding issues "related to possible military dimensions" to Iran's nuclear programme.
"We also hope that Iran will allow us to go to the site of Parchin," Nackaerts told journalists at Vienna airport before departing for Tehran. "If Iran would grant us access, we would welcome that chance and we are ready to go."
Some members of his team - which included senior experts on Iran and nuclear weapons - carried metal cases apparently with the equipment they would need to inspect a site like Parchin. Typically, they would take earth and other samples there.
But Iranian atomic energy chief Fereydoun Abbasi-Davani gave no sign of any green light to go to Parchin. The IAEA officials "will come to Tehran and they will have discussions with our representatives here", he told Iran's Mehr News Agency.
IAEA TRIP MAY BE EXTENDED?
Western diplomats say they are not optimistic about a breakthrough in this week's discussions, since a series of meetings since January have failed to make any progress.
But they do not rule out that Iran, under tightening Western sanctions damaging its oil-dependent economy, will offer some concessions in an attempt to relieve international pressure.
"I have no reason to believe there will be any significant progress but it would be nice to be pleasantly surprised," one envoy said, adding he did not believe Iran had given any indication that access to Parchin might be possible.
The IAEA wants Iran to allow its inspectors to visit sites, interview officials and study documents as part of an inquiry - snarled by Iranian non-cooperation since 2008 - into suspected past, and possibly current, nuclear weapons research.
Iran says its nuclear programme is entirely peaceful and rejects international demands to curb atomic activity that could have both civilian and military purposes.
It says it must agree a framework for the inquiry with the Vienna-based IAEA before providing the requested access. Western officials see this condition as procedural stalling by Iran.
Iran's Kayhan newspaper - believed to reflect the views of Supreme Leader Ayatollah Ali Khamenei - suggested the Iran-IAEA meeting could be extended beyond the planned one day of talks.
"News has reached Kayhan that indicates that if the negotiations are successful, there is the possibility their (the IAEA delegation's) trip will be lengthened," it said.
The IAEA talks with Iran are separate from - but complementary 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.