"I hope very much we will get constructive, positive answers to the documents that we sent to them," he said, referring to proposals sent to Iran in June.

"I hope this will allow us to get engaged in meaningful negotiations," he added.

Solana is due in Geneva on Saturday for talks with Tehran's nuclear negotiator Saeed Jalili as part of continuing efforts to end what the West fears is a covert nuclear weapons drive.

Also present will be representatives from the P5 plus one group: Britain, China, France, Russia, the United States -- the five permanent members of the UN Security Council -- and Germany.

And in what amounts to a major foreign policy shift, US Under Secretary of State William Burns will attend the talks: the highest-level meeting between the two foes in three decades.

White House spokeswoman Dana Perino said Burns would go to Geneva "to listen" to Tehran's reply to an incentives offer for freezing uranium enrichment. "We are not there to negotiate," she stressed.

On June 14, Solana presented a package of proposals from the world powers, offering Iran negotiations on technological incentives if it suspended enrichment.

On June 23, the European Union stepped up the pressure, agreeing fresh sanctions, notably banning the country's largest bank, Bank Melli, from operating in the bloc.

Solana and the Western representatives hope that Saturday's meeting will clarify Iran's response.

Iran last week intensified tensions in the nuclear standoff by staging two days of missile tests, which included the firing of a missile that it says can reach Israel.