A US Navy warship fired a warning flare to wave off an Iranian Revolutionary Guard speedboat coming straight at it during a tense encounter in the strategic Strait of Hormuz, officials said Tuesday. The incident on Monday involving the Guard and the Navy comes as tensions remain high over stalled negotiations over Iran’s tattered nuclear deal with world powers and as Tehran enriches uranium closer than ever to weapons-grade levels under decreasing international oversight. Meanwhile, the United Nations’ nuclear watchdog said Iran now plans to enrich uranium through a second set of advanced cent…