The parent companies of T-Mobile USA (TMUS) and Sprint Corp. (S) have been engaged in serious merger talks, CNBC reported Tuesday. 

T-Mobile parent company Deutsche Telecom (DTEGY) would emerge as the majority owner if the United States' third and fourth largest mobile carriers did complete a deal, according to CNBC sources. 

T-Mobile and Sprint have flirted with a merger for years and sources say that any potential deal between the two companies now is still weeks away. 

A deal would also face stiff regulatory scrutiny due to the market share each company possesses. 

T-Mobile shares were up 4.4% to $64.48 Tuesday afternoon while Sprint shares were up 7.87% to $8.28 per share. 

Watch: T-Mobile Targets Verizon With #GetOutofTheRed Limited Time Offer

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