LAUSANNE, Switzerland (AP) — Negotiations over Iran's nuclear program picked up pace on Saturday with the foreign ministers of France and Germany joining U.S. Secretary of State John Kerry in talks with Iran's top diplomat ahead of a looming end-of-March deadline for a preliminary deal. Iran says its nuclear ambitions are purely peaceful, but other nations fear it is seeking to develop weapons. Progress has been made on the main issue — the future shape of Iran's uranium enrichment program, which can produce material for energy, science and medicine but also for the fissile core of a nuclear weapon. Officials have told The Associated Press that the U.S.