Vienna, Austria ? A senior U.S. envoy will sit eye-to-eye for the first time Saturday with a top Iranian nuclear negotiator, a sharp reversal in U.S. policy that aims to entice Tehran into ending activities that could be used to make atomic weapons.

The move to send Undersecretary of State William Burns to the Geneva nuclear talks has raised the hackles of Washington hardliners who say it signals U.S. weakness. But supporters insist because both Tehran and the United States want to ease tensions, the move could breathe life into deadlocked nuclear talks.

On the eve of the meeting, French Foreign Minister Bernard Kouchner said the talks offered hope for a peaceful solution to the standoff over Tehran’s nuclear program. But he also expects no quick changes from Iran, which has said “the essentials” – an apparent reference to suspending uranium enrichment – will not be on the table.

Initially, supporters of the negotiations say, the U.S and its allies could agree to stop pushing for new U.N. sanctions if Tehran stops expanding its uranium-enrichment capacities – setting the stage for fuller negotiations and what the West hopes will be agreement from Tehran to dismantle its enrichment program.