* IAEA believes Iran held nuclear-relevant tests at Parchin
* Iran says it is a conventional military facility
* Western diplomats suspect Iran is cleaning up site
By Fredrik Dahl
VIENNA, Nov 21 (Reuters) - Iran has been hauling dirt to a site that international nuclear experts want to inspect, Western diplomats said on Wednesday, saying the findings were based on satellite images and they reinforced suspicions of a clean-up.
They said the pictures, presented during a closed-door briefing for member states of the International Atomic Energy Agency (IAEA), suggested Iran was continuing to try to hide incriminating traces of any illicit nuclear-related activity.
The allegations come a few days after the IAEA said in a report on Iran's nuclear programme that "extensive activities" undertaken at the Parchin site since early this year would seriously undermine its investigation, if and when inspectors were allowed access.
The U.N. agency believes Iran may have conducted explosives tests that could help develop nuclear weapons at Parchin. Iran denies this, saying Parchin is a conventional military complex.
The latest satellite image, dated Nov. 7, showed what appeared to be piles of dirt, according to diplomats who attended the briefing by chief U.N. inspector Herman Nackaerts.
"They have been scraping the earth. Now they obviously want to put down new earth," one of them said, speaking on condition of anonymity. "There are piles of them that you can see."
Iran's mission to the IAEA was not available for comment.
The IAEA report, issued on Friday, listed activities observed at Parchin since February, including the removal of "considerable quantities" of earth at the location in question and its surrounding area, which it said covered 25 hectares.
This had been followed by "further removal of earth to a greater depth ... and the depositing of new earth in its place."
Earlier IAEA reports have described the demolition of buildings at Parchin and other apparent clean-up work. The building where the IAEA believes the tests were carried out has been covered up, it says.
The Islamic state denies Western accusations that it is seeking to develop the capability to make nuclear bombs. But U.N. inspectors suspect that research and experiments relevant to nuclear weapons development have been conducted in the past, and possibly continues.
IAEA chief Yukiya Amano has pressed Iran to grant his inspectors immediate access to Parchin, a sprawling facility southeast of the capital Tehran. The IAEA also wants access to other sites, as well as to officials and documents.
"There are lots of activities (at Parchin) since the beginning of this year and some of these activities are quite important," Amano said during a visit to Paris this week.
Tehran says it must first reach a broader agreement with the IAEA on how the Vienna-based U.N. agency should conduct its investigation into alleged nuclear bomb research in the Islamic state before it can possibly be allowed to visit Parchin.
A series of meetings this year between the IAEA and Iran, the most recent in August, has failed to make progress in allowing the U.N. agency to resume its long-stalled inquiry.
The two sides will meet again on Dec. 13 but Western diplomats say they are not optimistic about any breakthrough.
The IAEA's talks with Iran are separate - but are still closely linked to - efforts by six world powers to diplomatically resolve the decade-long nuclear dispute with Iran that has raised fears of a new war in the Middle East.
In Brussels on Wednesday, the six powers - the United States, France, Germany, Britain, Russia and China - said they were committed to holding a new round of negotiations with Iran as soon as possible.