Tunisia’s powerful UGTT union on Tuesday called a national strike in June in public services and state firms after the government refused to increase wages, an escalation that may hinder the government’s efforts to reach a deal with the International Monetary Fund. Tunisia faces its worst financial crisis and is seeking a $4 billion loan from the IMF seen as necessary to ward off national bankruptcy, in exchange for unpopular reforms, including food and energy subsidies cuts and wage freezes. With more than a million members, the UGTT is Tunisia’s most powerful political force. The strike on J…