Secretary of State John Kerry signaled Wednesday that Iran had to 'get serious' about addressing its nuclear program.
Kerry's comments came just weeks before a scheduled meeting between Iran and the five members of the UN Security Council and Germany.
Kerry, who was meeting with his Canadian counterpart John Baird, said Iran knew what it needed to do to address concerns, said AFP.
He said that the US was still willing to deal with Iran using diplomacy.
"We are prepared to let diplomacy be the victor in this confrontation over their nuclear program," Kerry said to reporters, said the Associated Press.
"The president has made it clear that he is prepared to talk about a peaceful nuclear program."
It was Kerry's first comments on Iran since he moved into the State Department last week.
Kerry indicated that Iran's recent announcement that it would speed up the enrichment of uranium was unacceptable.
He also reiterated that the US would not tolerate a nuclear Iran.
"The president has made it clear that his preference is to have a diplomatic solution, but if he cannot get there, he is prepared to do whatever is necessary to make certain that Iran does not have a nuclear weapon," he said, according to the Associated Press.
Iran has been hit with crippling sanctions that have left its economy in crisis.
The Iranian government continues to deny that it is enriching uranium for nuclear weapons.