The United States said Wednesday it hoped for high-level talks in the coming weeks with Iran and five other world powers that are working with Washington to try to curb Tehran's nuclear ambitions.

US optimism for such talks came after Iran vowed Tuesday to press ahead with its atomic program in the face of tough new EU sanctions while at the same time expressing readiness to resume nuclear talks.

State Department spokesman Philip Crowley said "we hope to have the same kind of meeting in the coming weeks that we had last October," in which Iran was urged to accept a nuclear fuel swap as a confidence building measure.

"There have been contacts between Iran" and the European Union's high representative, Catherine Ashton, about a "prospective meeting," he said.

"I've got nothing to announce here but... we obviously are fully prepared to follow up with Iran on specifics regarding our initial proposal... involving the Tehran Research Reactor" and related issues.

Under the deal from last year, Iran would ship most of its low-grade uranium to France and Russia so that it could be further enriched and returned to the Tehran Research Reactor to make medical isotopes.

The deal, backed by the International Atomic Energy Agency (IAEA), would buy time amid US concerns that Iran seeks to enrich uranium to levels needed for a nuclear bomb -- even though Iran insists its program is peaceful.

Crowley did not say specifically why he was optimistic about the holding of a meeting among senior officials from Iran, the United States, Russia, China, France, Britain and Germany.

However, he said the United States had received a copy of a letter from Iran given in the last few days to the IAEA, the UN nuclear watchdog, and said US officials were reviewing it.

The watchdog said Monday that Iran has responded to queries raised by the Vienna group of diplomatic powers over a nuclear fuel swap deal proposed in May by Brazil, Turkey and Tehran and based on the original October proposal.

But Washington, while still holding the door open to negotiations, effectively rejected what it saw as a bid by Tehran to thwart a fourth set of UN Security Council sanctions that were imposed in New York on June 9.

Since the imposition of those sanctions which targeted Iran's military and financial sectors, the United States, Canada and the European Union have taken further punitive steps of their own.

A senior State Department official, speaking to reporters on the condition of anonymity, implied that the chances of talks are higher now than in June.

"Some of the gestures by Iran were really intended to try to halt the (sanctions) process going on in New York," the official said. "Now that that process has completed, if Iran wants to engage on these subjects, we are more than happy to have that conversation."

In talks earlier this year with Brazil and Turkey, US Secretary of State Hillary Clinton argued that Iran would only seriously negotiate when it feels the bite of sanctions while Brasilia and Ankara said more time was needed for diplomacy to work.