BT has entered into talks with Spanish firm Telefonica about acquiring its O2 mobile network, the Spanish website El Confidencial reports.
The UK telecoms firm said it was in talks with "shareholders in two UK mobile network operators, of which one is O2, about a possible transaction in which BT would acquire their UK mobile business".
According to the Financial Times, the other UK network being offered to BT is EE.
In a statement sent to the Spanish stock market, Telefonica said: "Telefonica informs that, although it is in talks with British Telecom, these talks are in a highly preliminary phase and there is no certainty that a transaction will take place."
In 2002, BT let go of O2, which was then called BT Cellnet. In 2005, O2 was acquired by Spain's Telefonica for £17.7bn.
Last year, Telefonica sold a number of its assets to reduce debt and improve its credit rating.
"We continue to develop our own plans for providing enhanced mobile services to business and consumer customers, in line with our previous announcements," a BT spokesperson said.
Earlier this year BT announced it was promoting its IT security capabilities to external customers for the first time.
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