Syria has invited UN inspectors to visit in a probe of allegations that a remote building destroyed by IAF fighter jets was a nuclear reactor built secretly with North Korean help, the International Atomic Energy Agency said Monday. Announcing the planned June 22-24 visit, IAEA head Mohamed ElBaradei also criticized Iran for stonewalling his investigations into allegations that the country worked on a secret nuclear weapons program. His comments to the agency's 35-nation board reflected the main focus of a board meeting that opened Monday - Iran's nuclear defiance and suspicions that Syria tried to build a plutonium-producing reactor and tried to cover up after the building was flatted in September by Israel. Neither the United States nor Israel told the International Atomic Energy Agency about the Syrian site until late April, about a year after they obtained what they considered to be decisive intelligence: dozens of photographs from a handheld camera that showed both the interior and exterior of the mysterious compound in Syria's eastern desert. Since that time, Syria had not reacted to repeated agency requests for a visit to check out the allegations, using the interval to erect another structure over the site - a move that heightened suspicions of a possible cover-up. ElBaradei repeated his criticism of Israel and the United States in announcing the Syrian visit, taking Washington to task for waiting so long to brief him on its suspicions, and Jerusalem for its air strike. Diplomats have recently suggested that the Americans may have waited even longer, telling The Associated Press that Washington may have had indications of Syrian plans more than five years ago. They demanded anonymity because their information was confidential. "It is deeply regrettable that information concerning this installation was not provided to the agency in a timely manner and that force was resorted to unilaterally before the agency was given an opportunity to establish the facts," ElBaradei said. His comments to the closed meeting were made available to reporters. While steering clear of a judgment on the issue, ElBaradei also noted Damascus "has an obligation to report the planning and construction of any nuclear facility to the agency." He did not say whether his inspectors would be granted access to the site, but a senior diplomat familiar with the details of the planned visit said agency personnel would visit the facility. ElBaradei was also outspoken on Iran, in connection with its probe of activities that point to a possible clandestine weapons program, repeating comments he first made in a report last week with even more clarity. "It is regrettable that we have not made the progress we had hoped for with respect to ... clarification of the cluster of allegations ... relevant to possible military dimensions to Iran's nuclear program," he said, adding that the alleged activities "remain a matter of serious concern." "Iran has not provided the agency with all the access to documents and to individuals requested ... nor has Iran provided the substantive explanations required to support its statements," he said. "Such clarifications are critical to an assessment of the nature of Iran's past and present nuclear program." ElBaradei also said his agency "understands that Iran may have additional information" it was withholding from IAEA experts - an allegation also made in his report last week to the agency board and the UN Security Council. Since launching its probe into the allegations last year, the International Atomic Energy Agency has asked - in vain - for substantive explanations for what seem to be draft plans to refit missiles with nuclear warheads; explosives tests that could be used for a nuclear detonation; military and civilian nuclear links and a drawing showing how to mold uranium metal into the shape of warheads. Iran remains defiant, dismissing evidence from the US and other board members purportedly backing the allegations as fabricated. It is also under fire for defying three sets of Security Council sanctions and continuing to enrich uranium - a process that can generate both nuclear fuel and the fissile material for the core of nuclear warheads.