"This is part of a pattern of deception and lies on the part of the Iranians from the very beginning with respect to their nuclear program," he said.
"So it's no wonder that world leaders think that they have ulterior motives that they have a plan to go forward with nuclear weapons," The Jerusalem Post quoted him, as saying.
"If this were a peaceful nuclear program, why didn't they announce this site when they began to construct it?" Gates asked. "Why didn't they allow International Atomic Energy Agency inspectors in from the very beginning?"
In a second interview with CNN, Gates said that while the US did not rule out use of force against Iran, but added that diplomacy and sanctions could still prove effective.
He added that any military option would only delay the Iranian nuclear program. International pressure on Iran has increased in recent days, after new revelations surfaced that the country has been building a secret uranium enrichment plant.
Image: US Defence Secretary Robert Gates