The State Department confirmed Wednesday that  senior U.S. diplomat William Burns will join in a critical meeting Saturday in Geneva with Iran's nuclear negotiator. Iran is expected to give its reply to an offer of incentives if it suspends uranium enrichment. VOA'S David Gollust reports from the State Department.

US Undersecretary of State for Political Affairs William Burns testifies during hearing on Capitol Hill, in Washington, 09 Jul 2008

Officials say Undersecretary Burns, the third-ranking State Department official, will not have separate talks with Iranian negotiator, Saeed Jalili, but they say his presence will underscore U.S. good-faith on  the incentives initiative.

In a significant policy shift, leaked to U.S. media outlets late Tuesday, it was decided that Burns will join European Union chief diplomat Javier Solana and other big-power diplomats at the Geneva meeting.

The Bush administration had previously refused direct contacts with Iran on the nuclear issue unless it agreed first to suspend its uranium-enrichment program, which U.S. officials believe is weapons-related.

In Geneva, the Iranian negotiator is to give Tehran's formal response to a so-called refreshed incentives package presented by the five permanent U.N. Security Council member countries and Germany, the P-Five-Plus-One.

In it, Iran is offered benefits including assistance on civilian nuclear power and access to new passenger aircraft if it suspends its enrichment program and enters negotiations on a permanent end to its suspect nuclear activities.

An affirmative Iranian response would also mean the suspension of U.N. Security Council sanctions against Tehran.

At a news briefing, State Department Spokesman Sean McCormack said Burn's presence at the table is a symbolic change, but not a shift in the basic U.S. position that Iran must stop enrichment if it is to realize benefits, including dialogue with the United States.

"Is this a new tactic, if you will? Yes. Does it send a signal? Yes. Is the substance any different? No. So I would argue that the fact that ambassador Burns will attend the meeting underscores, as I said, the commitment to diplomacy. The fact that if the Iranians take the step of suspending their enrichment-related activity, they will see an American at the table. They will see the Secretary of State, for negotiations," said McCormack.

McCormack reaffirmed that EU diplomat Solana is prepared to begin so-called "pre-negotiations" with Tehran even before enrichment is stopped.

Under what is being called a "freeze-for-freeze" arrangement, Iran would agree to stop adding to its array of enrichment centrifuges at the Natanz nuclear plant, while the P-Five-Plus-One would not add to Iran sanctions.

After six weeks, in that scenario, Iran would suspend enrichment and full-scale negotiations would begin.

U.S. and Iranian diplomats have rarely met since formal  relations were broken off after Iran's 1979 Islamic revolution. McCormack said Undersecretary Burns' personal interaction with Iranian negotiator Jalili in Geneva, if any, will be limited.

"There aren't going to be any one-on-one meetings," said McCormack. "I'm sure that Ambassador Burns will be polite, as we have been in other encounters with Iranian diplomats in a variety of different venues when we have encountered them. Instructions to U.S. diplomats, if you do find yourself in a position of encountering an Iranian diplomat, is that you are to be polite, but not engage in any substantive discussion and that I assume will be Bill's instructions here."

Secretary of State Condoleezza Rice has said that if Iran stops enrichment, decades of U.S. policy would be scrapped and she would be prepared to engage her Iranian counterpart on any issue, in any venue.