"What is important for us is with what approach they come to the talks. If it is with a constructive approach, and that they refrain from past mistakes, then for sure we will have constructive talks," he was quoted as saying by the official IRNA news agency before leaving Tehran for Geneva.

Jalili on Saturday is to meet the European Union foreign policy chief Javier Solana to discuss a package of incentives offered by world powers to Tehran.

And, in a major policy shift by Washington, US Under-secretary of State William Burns will be at the talks.

"In these talks we will discuss the common points of the two packages and also both sides' ideas on continuing the talks," Jalili added.

He was referring to the incentive package offered by the world powers and to Iran's own package which is aimed at "solving the world problems."

Jalili, who heads Iran's Supreme National Security Council, is accompanied on this trip by Ali Bagheri, the council's deputy head in charge of international affairs.

Iran had said that the talks are aimed at finding "a framework" for future talks by the negotiating parties.

Foreign Minister Manouchehr Mottaki on Friday welcomed as "positive" the US presence at the Geneva talks.

The US participation is "a new positive approach," Mottaki said after talks in Ankara with his Turkish counterpart Ali Babacan.

"I hope this progress (in the format) will also reflect on the content of the talks," he said. "If the negotiations continue in this way, I hope there will be a positive outcome."

Tehran's Friday prayer leader in a sermon broadcast live on state radio that Iran "will show goodwill," if it is reciprocated.

"From the beginning we said that we seek constructive talks, which must be without precondition and threat. We believe that if talks are done with goodwill then Islamic Iran will come forward with goodwill and the talks will have results," senior cleric Ayatollah Ahmad Khatami said.

"But if they are held under the influence of the Zionist regime or the arrogant powers, then just as before it will be fruitless," he warned.

Earlier this week, US officials said that the "new tactic" of sending a senior official to the talks amounted to sending a signal to Iran that Washington wanted a negotiated settlement to the deadlock over Iran's refusal to bow to international demands.

Washington has long said it will not negotiate with Iran until it first suspends uranium enrichment and insisted on Wednesday that Burns was travelling to Geneva to listen to Iran's response and not negotiate.

Nonetheless, it will be the first time that the United States, which severed relations with Iran in 1980 after the Islamic revolution, will be present in the negotiations aimed at persuading Tehran to freeze uranium enrichment.

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.

Western countries suspect that Iran is secretly trying to develop the atomic bomb and the United Nations has slapped several sets of sanctions on Tehran over its refusal to halt enrichment.

Iran vehemently denies seeking nuclear weapons, insisting that its programme is designed to provide energy for its growing population for the time when its reserves of fossil fuels run out.

On Thursday, Solana and Burns met in Brussels in preparation for the weekend talks.

"Mr Solana told Mr Burns that his participation could only have a positive impact," said spokeswoman Cristina Gallach. "We hope the Iranians are going to understand the importance of this decision" to attend.

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