WASHINGTON (Reuters) - U.S. Defense Secretary Jim Mattis will again meet his Turkish counterpart next week in Europe, the top U.S. general said on Monday, describing regular U.S. efforts to address Turkish concerns over a U.S. decision to arm Kurdish fighters in Syria. U.S. Marine General Joseph Dunford, chairman of the Joint Chiefs of Staff, said Mattis also wrote a detailed letter to Turkey last week to provide a “routine update” on U.S. efforts in Syria.  