"Our goal is to achieve a verifiable agreement that does not allow Iran to obtain a nuclear weapon," White House Press Secretary Jay Carney told reporters.
"We've said, obviously, that the window is open for us to pursue this option, to achieve our goal of not allowing Iran to possess a nuclear weapon, and we're going to aggressively pursue that while the window is open," he said on the eve of the next round of talks between Iran and the P5+1 (the US, Britain, France, Russia, Chinaplus Germany) in Geneva.
"But it won't remain open indefinitely," he said, issuing a subtle warning to Iran to accelerate the process to address the concerns of the international community on its nuclear programme.
"So we're obviously going into this eyes wide open, but as we've discussed in the past, we need to take advantage of this opportunity to see if, in fact, Iran is serious about addressing the international community's concerns when it comes to its nuclear weapons program in a way that is verifiable for the United States and the whole international community that's concerned about it," he said.
Under Secretary of State for Political Affairs Wendy R Sherman is leading the US delegation for the talks with Iran.
'History of mistrust between Us and Iran is deep'
Responding to questions on the anti-US protests in Iran, Carney said, "the history of mistrust between the United States and the Islamic Republic of Iran is deep and it will not be erased overnight."
But what they are doing now is not about trust, he said.
"We're engaged in serious and substantive negotiations that offer the possibility that we can stop the advance of Iran's nuclear program, gain more transparency into their nuclear activities, and negotiate a long-term, comprehensive solution that resolves the international community's concerns about Iran's nuclear program," he said.
Carney said the US believes that the vast majority of Iranians would prefer a better relationship with the West and would prefer the benefits of that better relationship with the West, including the economic benefits of rejoining the international community, to the current status quo.