VIENNA – Iran’s nuclear chief said Monday that “terrorists and saboteurs” might have infiltrated the International Atomic Energy Agency in an effort to derail his nation’s atomic program. It was Tehran’s harshest attack on the integrity of the U.N. organization and its investigation of allegations that Iran is striving to make nuclear arms.

Fereydoun Abbasi also rebuked the United States in comments to the IAEA’s 155-nation general conference, reflecting Iran’s determination to continue defying international pressure aimed at curbing its nuclear program and nudging it to cooperate with the IAEA inspection.

Revealing what he said were two sabotage attempts on his country’s nuclear program, he challenged the perpetrators to launch new attacks, saying his country is determined to learn how to protect its interests through such assaults.

The defiant speech was bound to give a greater voice to hardline Israeli leaders who say pressure has had no effect on Iran.