Vodafone said on Sunday it was in advanced talks with Verizon Communications about the sale of its 45% stake in Verizon Wireless for $130 billion in a mix of cash and shares.
"There is no certainty that an agreement will be reached," the British group said in a statement. "A further announcement will be made as soon as practicable."
Reuters had earlier reported that the two groups were due to announce the terms of the deal on Monday, pending board approval.
The board of Vodafone was set to meet on Sunday while Verizon's was due to meet on Monday morning New York time.