Speaking to reporters on a flight to Hawaii, she said the administration was contemplating sanctions that would target the Tehran leadership's political and commercial base, but added no decision had been made.
"The P5-plus-1 will reconvene in New York at the end of this week, and they will be exploring the kind and degree of sanctions that we should be pursuing," Clinton told reporters on her way to Hawaii.
The P5-plus-one are the five permanent veto-wielding members of the UN Security Council plus Germany, the group that has been reaching out to Iran in a bid to force the regime to halt its uranium enrichment.
At the end of last year, Clinton and other senior US officials signaled growing impatience with Iran's continued balking at a United Nations nuclear watchdog offer to build confidence with the international community.
The United States has backed the offer, a UN International Atomic Energy Agency (IAEA) proposal to ship abroad low-grade nuclear fuel so it can be further enriched and returned to refuel a Tehran medical research reactor.
Though not completely closing the door on the engagement policy which President Barack Obama has pursued toward Iran since taking office last year, Clinton elaborated on the kinds of sanctions she thought would be effective.
"It is clear that there's a relatively small group of decision-makers inside Iran," Clinton said.
"They are in both political and commercial relationships and if we can create a sanctions track that targets those who actually make the decisions, we think that is a smarter way to do sanctions," Clinton said.
"But that is all yet to be decided upon," she said.
Obama gave Iran until the end of the year to take up his offer of engagement, but US officials have indicated there was no hard and fast deadline.
She appeared to dismiss reports that a diplomatic solution was in the works.
"We get a constant flow of feelers from the Iranians on approaches that they might consider," Clinton said when asked if there indications that the Iranians are more conciliatory.
But she gave no sign the US would budge from its position.
"We support the IAEA Tehran research reactor proposal," the chief US diplomat said.
"We think that best represents the international community and the kind of approach we think is likely to be a confidence builder for the rest of the world concerning Iran's nuclear program," she said.
Such a move would buy breathing room as the big powers try to halt Iran's uranium enrichment — which the West fears masks a drive to build a nuclear bomb.
Denying the charge, Iran says it seeks peaceful uses of nuclear energy.
It was not immediately clear whether the United States could build the political support needed to impose another set of sanctions. Three sets of UN sanctions have already been slapped on the Islamic republic.
Last week, China's UN ambassador Zhang Yesui said it was too early to contemplate new sanctions against Iran over its refusal to halt sensitive nuclear fuel work, and called for more diplomacy.
China and Russia have been more reluctant to impose sanctions on Iran than the other four powers.
