VIENNA: The head of the International Atomic Energy Agency warned yesterday that he cannot guarantee that Iran is not running a secret nuclear program, comments that appeared to reflect a high level of frustration with stonewalling of his investigators.

A senior Iranian envoy accused the United States of trying to use the IAEA as a tool in Washington’s confrontation with Tehran. Iran, he said, has demonstrated full cooperation with the agency. Allegations of nuclear weapons work by Tehran is based on forged documents and the issue is closed, the envoy said.

The two men spoke at the start of a meeting of the 35-nation board of the IAEA. With time running out before Tehran develops potential nuclear weapons capacity, some worry that Israel or the US might resort to military strikes if they believe all diplomatic options have been exhausted. And with Tehran showing no signs of giving up uranium enrichment or heeding other international demands, the diplomatic window appears to be closing.

IAEA Director Mohamed El-Baradei said Iran’s stonewalling of his agency was a “serious concern.”

“Iran needs to give the agency substantive information” to clear up suspicions, he told the closed board meeting, in comments made available to reporters. He rejected the Iranian suggestion that the IAEA probe could expose non-nuclear military secrets, saying the IAEA “does not in any way seek to ‘pry’ into Iran’s conventional or missile-related military activities.”

“We need, however, to make use of all relevant information to be able to confirm that no nuclear material is being used for nuclear weapons purposes,” he said, urging Iran to “implement all measures required to build confidence in the exclusively peaceful nature of its nuclear program at the earliest possible date.” If Tehran fails to do so, the IAEA “will not be able to provide credible assurances about the absence of undeclared nuclear material and activities in Iran,” he said.

Outside the meeting, an indignant Ali Ashgar Soltanieh, the chief Iranian delegate to the IAEA, rejected suggestions his country was hiding something, and accused Washington of hijacking the agency for an anti-Iran campaign. “The international community and all member states of the IAEA are frustrated with this kind of United States actions in the IAEA,” he told reporters. “The Americans are every day isolating themselves. Iran is of course very advanced in missile activities and technology,” he said. “But there is no activity at all related to nucleareapons.”