By Phil Stewart, Idrees Ali and Jonathan Landay WASHINGTON (Reuters) – U.S. President Joe Biden’s emerging strategy on Yemen aims to weaken the Houthi militants but stops well short of trying to defeat the group or directly address Iran, the Houthi’s main sponsor, raising risks of prolonged conflict, experts say. The strategy – a blend of limited military strikes and sanctions – appears aimed at preventing a wider Middle East conflict even as Washington seeks to punish the Houthis for their attacks on Red Sea shipping. But it is unclear whether it will accomplish Biden’s main goal: halting the…