Vodafone Group and Cingular Wireless have started a bidding war for AT&T WIreless, which could take another two weeks to resolve.
Both companies had put in similar bids of around $35bn each.
Bidding had been due to close last Friday, and sources close to the situation said a decision could be expected soon, but AT&T Wireless may now seek a second round of offers from the companies.
By submitting your personal information, you agree that TechTarget and its partners may contact you regarding relevant content, products and special offers.
Nextel Communications and NTT DoCoMo did not enter bids.
Vodafone has a 45% stake in Verizon Wireless, the largest mobile company in the US. If its AT&T bid proved successful, it would have to relinquish its Verizon stake.
Cingular is a joint venture between SBC Communications and BellSouth, and is the second largest mobile phone company in the US.