Recent satellite imagery of the controversial Parchin military site in Iran shows evidence of "considerable sanitization and earth displacement activity", indicating a possible Iranian cover-up of work related to nuclear weapons development, according to a report released by the Institute for Science and International Security on Wednesday.

The International Atomic Energy Agency believes that Parchin may be the location of a high explosives testing chamber used by Iran in suspected nuclear weapons development efforts. In February, the agency sought to inspect the site to determine whether military nuclear activity had taken place there. Iran has repeatedly refused to grant the agency access to the site, saying that access could only be permitted as part of a broader deal on issues dealing with military aspects of its nuclear program. Negotiations on such a deal have not borne fruit.

"Looking back, Iran’s negotiating strategy appeared aimed at stalling while it undertook a range of cleanup activities at the Parchin site," the report, authored by David Albright and Robert Avagyan, asserted.

A commercial satellite image taken of Parchin on July 25 shows "stark differences" from an image of the site taken on April 9.

"The entire area surrounding the buildings appears to have been bulldozed, covered, and flattened," the report read. "The only remaining traces of activity are the apparent base of one of the demolished buildings and earth piles formed as a result of earth removal and displacement."

According to the report, the changes at the site undermine Iran's claim that its nuclear program is intended for peaceful purposes only. The authors called on the IAEA Board of Governors to refer the matter to the U.N. Security Council if Iran does not "concretely" address the issue of the military components of its nuclear program by a September meeting of the board.

After meeting with U.S. Defense Secretary Leon Panetta on Wednesday, Prime Minister Benjamin Netanyahu said that sanctions and diplomacy had not yet had any impact on Iran's nuclear program.

Panetta reiterated his pledge that the U.S. was committed to preventing Iran from ever obtaining nuclear weapons.