"We certainly want to make clear that no one, despite the positive signs that we've seen, should expect a breakthrough overnight," White House Press Secretary Jay Carney told reporters at his daily news conference.
He was responding to questions on talks between Iran and the P5+1 (the US, France, Britain, Russia, China and German) on the Tehran's nuclear programme. On the first day, the Iranian delegation made a presentation and the P5+1 spent the day discussing the presentation.
"We're not going to negotiate this in public or go into the details of what was in their proposal," he said.
"I would simply say that after day one, we're hopeful that we will make progress in Geneva. But beyond that, I wouldn't characterise the presentation or the status of conversations," he said when asked about the Iranian proposals.
"These are very complicated issues -- in some cases, very technical issues. And as the President (Barack Obama) has said, the mistrust here is very deep. But we hope for progress in Geneva," he said.
Carney said US will continue to keep up the economic pressure on Iran.
"Although we appreciate the recent change in tone from the Iranian government on this issue, we will be looking for specific steps that address core issues, such as the pace and scope of its enrichment program, the transparency of its overall nuclear program and its stockpiles of enrichment," he said.
"The P5-plus-1 is seeking an agreement that ultimately resolves all of the international community's concerns about Iran's nuclear programme. While we negotiate, we will continue to keep up the economic pressure on Iran, which has brought about the occasion for at least the prospect of making progress," Carney said.