A Wall Street Journal report about a possible offer from Sprint Corp caused T-Mobile US Inc shares to rise the most in over a year, a Bloomberg article said. T-Mobile is the fourth biggest wireless carrier in the US while Sprint is the third-largest in the country.

The report said shares of T-Mobile US increased 8.6% to 27.64 in New York trading yesterday, December 13. This marked the biggest gain in one day since October last year. The stock has risen 39% in 2013.

Citing unnamed sources familiar with the matter, the WSJ report revealed that Sprint is already looking into antitrust concerns and may possibly make an offer in the first half of 2014. Should the deal pushes through, the US would only have three major mobile phone operators, which will cause regulators to be wary of the deal. Two years ago, AT&T Inc did not push through with a $39 billion bid for T-Mobile due to the opposition of the Federal Communications Commission and the US Justice Department, the report said.

BTIG Analyst Walt Piecyk told Bloomberg, "There is little chance for a Sprint/T-Mobile deal to get through regulators over the next two years." The WSJ report said Sprint has not yet finalized its decision whether to make an offer but depending how much stake the Overland, Kansas-based carrier intends, the deal could reach over $20 billion. As of yesterday's trading, the market valuation of T-Mobile was $22.1 billion, Bloomberg reported.

Verizon Wireless and AT&T lead the market in wireless customers, while profitability continues to challenge Sprint and T-Mobile, the report said. This has led to the suggestion by analysts and investors that the two companies combine to establish a third force in the industry.

The report added that if a deal between the two carriers would push through, it would extend the wave of mergers in the telecommunications industry. Earlier this year, Softbank Corp bought a majority stake in Sprint while MetroPCS Communications Inc was absorbed by T-Mobile.