Both telecom groups declined comment on the future of EE (Hatfield, UK) on Thursday. Last year they said they were conducting a "strategic review on the asset to consider different options, with an IPO as the preferred option".
Private equity groups, including U.S.-based KKR (New York City, NY, USA) and Europe's CVC Capital Partners (London, UK), have also been sounding out banks to raise money to mount a potential 9 billion to 10 billion pound ($14 billion to $15 billion) buyout of EE.
Such a bid would be ambitious for private equity given its large size, but interest from funds or from industry buyers could emerge in the coming months and affect the IPO plan, sector bankers have said.
The banks advising the joint venture's owners are expected to run a "twin track" process to evaluate options for a sale or listing of EE, according to one of the sources.
EE, formerly known as Everything Everywhere, has more than 27 million customers and competes with Telefonica's 02 brand
In October, it became the first operator in Britain to launch super-fast mobile data services, known as 4G. It added 201,000 net contract subscribers in the fourth quarter, a slowdown from 250,000 in the third quarter.
The group posted full-year adjusted core earnings of 1.41 billion pounds, broadly flat on the year before.
($1 = 0.6607 British pounds)
(Reporting by Leila Abboud, Sophie Sassard, and Harro Ten Wolde; Editing by Charlotte Cooper)