As a deadline approaches for Russia to resume supplying natural gas to Germany this week, European officials and executives are growing concerned about a cascading economic fallout that would spread across the continent should Moscow keep the tap shut. The Nord Stream pipeline that ferries gas from Siberia to Germany closed last Monday for annual maintenance that is expected to last 10 days. Many in the West fear that Moscow might prolong the closure, possibly permanently, and deprive Germany, Europe’s industrial powerhouse, of a key ingredient for its and its neighbors’ factories.