VIENNA - A US envoy accused Iran on Thursday of "systematically demolishing" a facility at the Parchin military site that United Nations nuclear inspectors want to visit as part of their investigation into suspected weapons research."Iran has been taking measures that appear consistent with an effort to remove evidence of its past activities at Parchin," senior US diplomat Robert Wood told the 35-nation governing board of the International Atomic Energy Agency (IAEA).Iran says Parchin is a conventional military site and has dismissed allegations about it as "ridiculous."Citing satellite imagery, Western diplomats have for several months said they suspect Iran is cleaning the site of any evidence of illicit nuclear activity, by tearing down buildings and removing soil.Wood called on Iran to grant the UN immediate access to Parchin. "If Iran has nothing to hide there, why did it begin altering the site as soon as the IAEA asked to visit?" he asked, according to a copy of his statement to the closed-door board session.He said it was "troubling that Iran is blatantly hampering the (IAEA's) ability to carry out its mandate by systematically demolishing the facility that has been identified by the IAEA as meriting inspection at the Parchin site."The IAEA suspects Iran has conducted explosives tests in a steel chamber at Parchin, possibly a decade ago, and has repeatedly asked Iran to grant it access to the facility.