The United States on Friday denied reports that former Spanish Prime Minister Felipe Gonzalez was acting as a mediator in the nuclear impasse between Washington and Tehran when he met with Iranian leaders this week. "I am not aware of any mediation efforts," State Department spokesman Sean McCormack said when asked about the meeting this week between Gonzalez and Iranian President Mahmoud Ahmadinejad. McCormack reaffirmed that Washington would not negotiate with Iran unless Tehran complies with a U.N. Security Council resolution demanding that it suspends uranium-enrichment and reprocessing activities. The Iranians know what they have to do, and we are waiting for them to do it, he said. Gonzalez, who led Spain from 1982 to 1996, met with Ahmadinejad this week as part of broader European efforts to convince Iran to freeze its enrichment program. The center-left El Pais newspaper, which is close to Gonzalez s Socialist Party, reported Friday that Gonzalez undertook mediation between Tehran and Washington at Iran's request. It said the former prime minister was working to bring closer the positions of Tehran and Washington.