Korea First Bank and its largest shareholder, Newbridge Capital, have reportedly joined Cerberus Fund to bid jointly for at least a 51-percent stake in Chohung Bank. An unidentified source in Seoul said Japan's Shinsei Bankhas also joined the U.S.-based Cerberus Fund in the bidding. Two other bidders are A-B-N Amro group and a consortium led by Shinhan Financial Group. The government, which controls 80 percent of Chohung, wants to sell part of its stake. It has shortlisted four bidders and allowed them to conduct due diligence on the bank. Chohung Bank's labor-union is opposed to a merger between Korea First Bank and Chohung Bank. Unionized workers have seized documents relating to the due-diligence process, vowing to stage a full-scale strike from next Wednesday. On Friday, the government said it'll not sell the stake before the December 19th presidential election.