Germany\'s main opposition Social Democrats (SPD) held a special convention on Sunday to vote on whether to launch formal negotiations with Chancellor Angela Merkel\'s conservatives on forming a grand coalition. SPD party leaders unanimously agreed on entering formal coalition negotiations with Merkel\'s Christian Democratic Union (CDU) and its Bavarian sister party the Christian Social Union (CSU) on Thursday. Then they have to seek the backing of 200 senior Social Democrats at the party meeting scheduled at 1000 GMT before the actual negotiations begin. Once the party convention agrees on the deal, formal coalition negotiations are expected to start on Wednesday, more than one month after the Sept. 22 elections ended. Merkel\'s CDU/CSU bloc won 41.5 percent of the vote in the election, leaving it by far the biggest party in parliament but still short of a ruling majority, necessitating its search for a coalition partner. Recent polls show most Germans support a repeat of the so-called \"grand coalition\" between the CDU/CSU and SPD, as in Merkel\'s first term in 2005-2009. However, both sides have been unwilling to compromise on key issues, including the level of a nationwide legal minimum wage.@ The SPD wants to introduce a national minimum wage of 8.50 euros (11.35 U.S. dollars) per hour. Merkel\'s party opposes the plan but supports deals struck by employers and trade unions at industry and regional levels. Merkel\'s spokesman Steffen Seibert said the chancellor and cabinet will officially resign Tuesday and act as caretaker government until a new cabinet is formed. Merkel warned on Friday that a new government may not emerge until December.