Fresh off its $20 billion deal with Japan’s SoftBank, Sprint (S) is reportedly plotting a takeover of rival T-Mobile US (TMUS), a bid that would join the country’s No. 3 and No. 4 wireless providers. While a combination between T-Mobile and Sprint has been speculated about in the past, such a deal would likely face obstacles from antitrust regulators that have nixed deals in this space in the past. According to The Wall Street Journal, Sprint is studying regulatory concerns and could launch a bid worth more than $20 billion in the first half of 2014. T-Mobile had a market cap of $20.4 billion entering Friday’s trading.