"The Iranians have the intention of having nuclear weapons," US Defense Secretary Robert Gates has said.
In an interview with ABC to be aired Sunday, Gates added that "the question of whether they have made a formal decision to move towards the development of nuclear weapons is in doubt."
"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."
"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 IAEA 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 the Islamic Republic, diplomacy and sanctions could still prove effective. He added that any military option would only delay the Iranian nuclear program.
"The reality is there is no military option that does anything more than buy time," Gates said. "The estimates are three years or so."
International pressure on Iran has increased in recent days, after new revelations surfaced that the country has been building a secret uranium enrichment plant.
Following the reveal, US President Barack Obama, French President Nicolas Sarkozy and British Prime Minister Gordon Brown made a statement at the G-20, demanding Iran quickly disclose all its nuclear efforts - including any moves toward weapons development - "or be held accountable."
Sarkozy said Iran has until December to comply or face new sanctions. Before that, the Iranians are to meet next week with the US and other major powers to discuss a range of issues including Iran's nuclear program.
"We will not let this matter rest," said Brown, who accused Iran of "serial deception."
Obama urged Iran to fully disclose its nuclear activities and said the IAEA must investigate the newly revealed site, saying, "The Iranian government must now demonstrate through deeds its peaceful intentions or be held accountable to international standards and international law."