Sprint is preparing a possible bid for T-Mobile US, reports The Wall Street Journal. If permitted by antitrust regulators, a potential merger between the two companies would result in just three major carriers in the United States.Sprint is studying regulatory concerns and could launch a bid in the first half of next year, the people said. A deal could be worth more than $20 billion, depending on the size of any stake in T-Mobile that Sprint tries to buy. Sprint hasn’t yet decided whether to move ahead with a bid. Going forward despite regulators’ concerns would be highly risky. Any pursuit of a bid by Sprint could be aimed at testing antitrust officials’ reaction to a deal, and a bad reaction could put an end to the effort.