Vienna, Austria ? The EU’s foreign policy chief and Iran’s senior nuclear negotiator tentatively agreed late Monday to meet this week in Vienna to try to bridge differences over Tehran’s nuclear program, U.N. and European officials said.

The officials, who demanded anonymity for discussing confidential information with The Associated Press, stressed the date and venue still could change despite initial agreement to meet Wednesday in the Austrian capital.

While word leaked last week that the Iranians had agreed to meet with the EU’s Javier Solana to explore potential chances of solving the impasse, the time and venue are officially being kept secret in an apparent attempt not to jeopardize any chance of their success.

At issue is Tehran’s refusal to consider freezing uranium enrichment, a potential pathway to nuclear weapons, despite a demand by the U.N. Security Council. On Thursday, the last day of a council deadline for Iran to suspend enrichment, the International Atomic Energy Agency confirmed that Tehran had failed to do so, despite the threat of U.N. sanctions.

The talks between Solana and Iran’s Ali Larijani are seen as the last chance to explore the possibility of a negotiated solution to the standoff before the council actively starts work on such sanctions.